(Lecture delivered to the Harvard
Engineering Society on 6 Oct. 1939)
The U.S.S. Squalus [SS-192], the newest model of submarine, while engaged in preliminary trials, sunk in 243 feet of water off the Isles of Shoals in North Atlantic waters on 23 May 1939. On 24 May, the living survivors, 33 in number were rescued, uninjured and healthy. As the sun was setting on September 13, 1939, a solemn procession of ships with colors at half mast let by the [Fleet Tug No.26] U.S.S. Wandank, steamed slowly into the Portsmouth, N.H. Navy Yard, with the stricken ship and the bodies of those who lost their lives.
Those were, briefly, the high lights of the concluding chapter of the story of 12 years of research and training by the Navy after the tragic loss of the S-4 [SS-109] in 1927. In the 33 survivors, the Navy paid a "dividend" on the time and money spent in preparedness.
In the Experimental Diving Unit at the Navy Yard, Washington, on the morning of 23 May, one of the divers had just emerged from the recompression chamber after having subjected himself to a test which was to be the final check of a long series of tests which established a new conception of decompression for divers. I remarked to Dr. Willmon that this was the final "spot" on the curve, and to be careful of the samples. The samples were never run. A telephone call from Commander Lockwood in Operations of the Navy Department said briefly these grim words "Squalus is down off Isles of Shoals, depth between 200 and 400 feet, have your divers and equipment ready to leave immediately." Within 2 hours the first group was in the air and speeding toward Portsmouth, N.H. By midnight the 5 officers and 20 enlisted men had arrived at the scene of the accident.
I shall never be able to record the various thoughts that flashed through my mind during that 150 mile an hour ride through the air to Portsmouth. My memory went back to the first lung experiments, thrills of ten years ago, to the long and tedious years spent in training submarine officers and enlisted men of the submarine service to use the lung; to the first diving bell, the cranky open bell that would dump and fall and half drown us if we were not careful, of the final design produced by Commander Allen R. McCann and the comfort that it was to operate. I recalled the hundreds of thrills encountered in training and developing this device. The dreaded hour was here! Would the dreams of the experimenter come true or would some quirk of fate cross up the plans and thus destroy all of this work? How many shipmates were waiting for the answer? What were they thinking? Were they too deep? Would the crude helium apparatus work if they were too deep for air diving. Dr. Behnke, who was riding with me in the plane remarked "I have a feeling that we'll do it." Inwardly I felt the same way.
Upon arrival on the scene I reported to Rear Admiral Cyrus W. Cole, the Commandant of the Navy Yard, Portsmouth, N.H., who was in charge at the scene of the accident. He was in the Sculpin [SS-191], a sister ship of the Squalus. The wind was blowing briskly and the seas were choppy. It was nearly midnight. After giving me the facts of the situation, he said "I will appoint you to take charge of the diving operations."
The Squalus was lying in 243 feet of water, slight list to port, down by the stern a few degrees. She was flooded aft up to the control room, which meant the after battery compartment, forward engine room, after engine room and after torpedo room were probably flooded.
Thirty-three of her crew were alive in the forward compartments, but all telephones to the after compartments were silent. The Squalus had dived about 9 a.m., on the 23rd. After leveling off at periscope depth a sudden rush of air was felt an immediately after, water was observed to be pouring in through the engine induction lines. Attempts to surface the submarine failed and the stern sunk out of control. When at an angle of nearly 60 degrees she hit bottom, the bow settled down to rest. The marker buoy in the forward torpedo room was released and picked up by the SCULPIN. The telephone in the marker buoy was manned.
While the Captain of the Sculpin, Lt.Cdr. Wilkin was talking to the Captain of the Squalus, Lieutenant Naquin, the cable parted and conversation had to be continued by the laborious process of hammering code signals on the hull. Obviously the power system had failed which meant that some sea water had leaked into the forward battery. This introduced the danger of chlorine gas. It was later learned that this was true, and that lungs were broken out and distributed to all survivors, for protection against gas and for escape if such action was decided upon.
The Captain reported all hands comfortable, but cold; pressure in the compartments was about 12.5 pounds above atmospheric; hand lanterns were being used for light, air clear of chlorine gas and excessive CO2 in the control room and torpedo room; battery compartment closed off except for the passage - (It lies between the other two).
The U.S.S. Falcon [ASR-2], one of the Navy Rescue vessels, Lieutenant G.A. Sharp, USN, commanding, was on her way from New London with the rescue chamber and would arrive shortly after daybreak on the 24th.
We told the Captain of the Squalus to rest as easily as possible, that the pressure in the compartments would not injure the men and that the Falcon would arrive about 6 am with the rescue chamber.
We kept in contact with Lt. Naquin, bearing in mind that delay meant danger if escape by use of "lungs" must be attempted. Escape by this means would become necessary if some developments made it dangerous for the men to remain in the compartments. This was a delicate situation, for delay in attempting escape might reduce the chances for successful operation of the lung because of the reduced strength of the men caused by gas, exposure, lack of sleep, and hunger. On the other hand, rescue by the rescue chamber is safer, and there is less chance of losing men.
Wind and sea were increasing, but when the Falcon arrived, four anchors were dropped in a square about 1500 feet on a side and she was moored in the center near the location of the Squalus. Some difficulty was experienced in getting the Falcon in position because of the dragging of the windward anchors. She was finally hauled as near to the correct position as we dared about noon and rescue operations commenced.
During the previous night the wreck had been snagged with a grapnel [grapple] by the [harbor tug] Penacook [YT-6] and it was the line to this grapnel (21 thread manila) that was used for sending down our first diver. We were not sure that the grapnel was attached to the wreck and if it was attached just where it might be located. This was worse than drawing to an inside straight. My first diver was a second class Boatswain's Mate on the Falcon, Sibitzky, over six feet tall and about 200 pounds of the Navy's best brawn. We dressed him in his 200 pounds of equipment and sent him down. Lady Luck smiled on us for he landed on deck and excitedly reported "I see the capstan." What more could we ask for? Our diver was within 6 feet of the hatch that we wanted to get into. We had filled that inside straight. He reported that the broken cable of the marker buoy lay across the hatch. This, he was able to move clear.
I must digress momentarily to explain that the forward and after hatches of our submarines are fitted for attaching the rescue chamber. They have a flat doughnut shaped plate welded to the hatch combing upon which the bottom of the chamber rests and a bail over the center of the hatch to which the haul down wire must be attached by the diver.
We made ready the end of the downhaul wire and slid it down the descending line to the diver. He got the end and promptly lost it so that we had to haul it up again and send it down a second time. This time he shackled it into the bail and was ready to come up.
Eleven years ago (1928) the first diving bells for rescuing men from submarines were designed by the Bureau of Construction and Repair, Navy Department. A curious quirk of circumstances led up to this incident. While in command of the submarine S-1 [SS-105], in 1926, I wrote to the Bureau of Construction and Repair and recommended the adoption of a diving bell for the purposes of rescuing entrapped personnel from submarines. The S-1 carried the only submarine airplane hanger in the Navy and I completed tests with a new type of plane during my tours of duty. This hanger was a tank 20 feet long and 6 feet in diameter. When I was relieved of command of the S-1, I went to the Navy Department, Bureau of Construction and Repair, for duty in the Submarine section. There I found my letter about the diving bell, unanswered. A short time later I handled a letter from the new commanding officer of the S-1, stating that the airplane tank was of no further use, requesting authority to remove it, and requesting disposition. I felt opportunity knocking and prepared a reply to send it to New York there to be cut in half and used to make two diving bells for experimental purposes.
In the meantime the S-4 was lost with all hands and the Navy was very much "on the spot" because of the loss of lives that might have been saved. The pressure of this incident forced favorable action on the diving bell project. After nearly two years of experimentation full of highly interesting results, the final bell was evolved and christened a "rescue chamber."
Upon completion of two years ashore in the Bureau, I was sent to sea in the reconditioned S-4 to carry out practical experiments and training with the rescue chambers for all of our rescue vessels. In the meantime, I had been perfecting the lung for individual escape and the training of submarine personnel in its use went hand in hand with the training of personnel to handle the rescue chambers. The development of the lung is a long story and will have to be told at some other time.
I have left the survivors waiting, but felt that some background for the introduction of the now famous rescue chamber was needed. This apparatus is a pear shaped steel chamber, the big end uppermost, seven feet at the greatest diameter and ten feet high. It is divided into an upper closed compartment and a lower open compartment by a horizontal bulkhead which has a water tight hatch in its middle. Surrounding the lower compartment is a ballast tank of a capacity just equal to that of the lower compartment. Inside the lower compartment is a reel with 400 feet of ½" steel wire on it. The reel is operated by a shaft leading into the upper compartment. The shaft is rotated by an air motor. On the bottom edge of the lower compartment a rubber gasket is embedded into a circular groove, so that when the chamber is brought into contact with a flat surface (the hatch ring) a water tight joint may be effected with the application of pressure. Attached to the upper compartment is an air supply and an atmospheric exhaust hose, wire wound for strength. Also electric cables for telephone and light are attached. A wire pendant for hoisting and lowering is shackled into a padeye on top. This wire is also used for retrieving the chamber in case of emergency.
To return to the rescue operations, two experienced operators, Harmon and Mihalowski, both divers from the Falcon entered the upper compartment and the chamber was lowered over the side. The end of the haul down wire had been unreeled and attached to the hatch by Sibitzky. With the lower compartment flooded, the ballast tank full and auxiliary cans full of water, the chamber floated with several hundred pounds of positive buoyancy. The auxiliary cans, 14 in number are carried in the upper compartment and are dumped as passengers enter so that the proper buoyancy will be maintained. Extra blankets, flashlight, hot soup, sandwiches and extra CO2 absorbent were taken aboard for delivery to the submarine.
Harmon reported ready and I told him to go down. He turned on the air motor and as the wire was taken in on the reel the chamber crept along the surface about one hundred feet from the point where it was lowered into the water. Then it gradually submerged looking like some sea monster as it sank from sight. Progress was reported continuously until finally the report "Hatch is in sight." Taking it slowly they hauled the chamber down until it was resting on the flat seat surrounding the hatch. The wire leading through a centrally located fair lead to the hatch bail, also centrally located, causes the gasket to come into contact with the seat evenly. The ballast tank is then flooded from sea and the lower compartment emptied by admitting compressed air. The seal of the gasket to the hatch is then accomplished by suddenly releasing the compressed air in the lower compartment through the hose leading to the atmosphere. Harmon reported the seal made and the hatch leading to the lower compartment opened. Bear in mind that the upper compartment is under atmospheric pressure. Thus the sea pressure exerts an enormous pressure on the gasket and the joint is absolutely watertight. The seating pressure in this case was about 175 tons. Four steel bolts were then attached to the hatch rings as a safety measure and the submarine hatch was opened. This was opened slowly so that such pressure that was in the submarine could be equalized with that in the chamber. Each move could be followed by listening on the telephone. When the submarine hatch was finally opened the dull thud of the hatch falling open was a thrill I cannot describe. Not a shout or cheer came over the phone. A few "wise cracks" such as "why the delay," "where in the hell are the napkins." The men had been trained and this was just like a drill. I ordered them to dump 1000 pounds of water from the auxiliary cans and load seven passengers. I wanted to make four trips, 7, 8, 9 and 9 in order to bring up the 33 survivors. I wanted to see how she carried the load with each trip, so planned on increasing the number by 1 each trip.
Harmon reported 7 passengers loaded, designated by the submarine's skipper, Lieutenant Naquin. Next he reported "hatch closed" and "ready to come up." I ordered him to "unbolt, flood lower compartment, and blow the ballast tank". This done, he reported "Seal broken, coming up." The air motor, in reverse, unreeling wire, chugged away and there gradually rising to the surface by its own buoyancy came the first load of lucky men, almost a routine drill for us but in the eyes of the outside world a miracle. We tried to appear calm and maybe others were but to me this was the most exciting moment of my life. 11 years of preparation, combating skepticism and constructing imaginary disasters, all telescoped into one moment, who could remain calm?
The chamber appeared first a green splotch beneath the surface then the war color and she was hauled alongside. The top hatch was opened and the 7 lucky men removed. I changed the operators for each trip.
Soon the second trip was made, and when the chamber returned to the surface with eight passengers it looked so heavy that I felt that it would not be safe to carry nine on the third trip. This was a blow for each trip meant greater risk; the weather might get too rough, the anchors drag - in fact any one of a dozen things might happen. However, it looked risky and I made my decision. Five trips I announced, and told Lt. Naquin to send up 8 in the third trip.
They were loading the 3rd bunch when Commander Sackett rushed aft to tell me that by mistake 9 men had been brought up in the 2nd trip. I felt a genuine relief and immediately told Naquin to send 9 the 3rd trip, leaving 8 for that eventful 4th trip. How fortunate this was, we did not realize at the time. The 4th trip was made to the bottom. The last eight including the Captain, traditionally the last to leave his ship, were loaded. All were secured and the return trip started. All of a sudden she stopped! McDonald, the operator said "The wire is jammed on the reel." Loose turns had allowed the hauling part of the wire to slip between the turns on the reel and jam. This emergency had been provided for and I told him we would heave on the retrieving wire and help clear it. While hauling on this wire, it started to strand, strands parted like fire crackers. We stopped hauling just before the last strand parted. This emergency had not been provided for. It was almost dark by now and the wind and sea were no better. In order to save what wire was left I told McDonald to flood his ballast tank slowly and I would lower the chamber to the bottom. This was done and fortunately there was enough slack in the downhaul wire to permit the chamber to reach the ocean bottom without turning over. It was necessary to send down a diver to detach the haul down wire from the hatch bail. Squire, a big 200 pounder from the Experimental Diving Unit at Washington was designated to do this. He was dressed, went down in the dark and reported that the wire was too taught to unshackle. We had to send him a pair of wire cutters. With these he cut the wire. This was a fine job and could have been done only by an expert diver and one who has lots of power in his arms.
The next step was to attach a new retrieving wire to the chamber. Duncan and then Clayton attempted to take a new wire down, but the darkness proved to be too much of a handicap. We used a lamp, but the extra cable fouled and we found ourselves in a serious situation with a diver fouled in the wire, the most dangerous kind of fouling in the diving business. We finally managed to get Clayton up and then I changed the plan and decided to use the stranded wire and have the chamber brought to the surface. I told McDonald to blow the ballast tank a little at a time, in fact 3 seconds each time I gave the word. In the meanwhile, I had about 10 men hauling on the wire by hand. The strand would hold this amount of hauling. If we could pull the wire up until the stranded portion was on deck, we could then get a secure hold on the good part of the wire. At last we had the chamber light enough to haul it in by hand and we hauled it to the surface where the last of the survivors were rescued after a trying wait of four and a half hours. All survivors were in excellent condition and not even a cold developed from their exposure of nearly 40 hours.
The next diver to go down was Lt. J.K. Morrison. He took the descending line aft to the after torpedo room hatch. This was a long hard dive. Morrison did the job but the pressure nearly got him. Diving on air to such depths is extremely hazardous because the compressed nitrogen of the air acts more or less as an anesthetic. Only the greatest will power and determination will see the diver through. Diver Baker then went down and attached the haul down wire to the after hatch. Strange to say, he too lost the wire once before he made it fast.
Badders and Mihalowski then went down in the rescue chamber to see if there was anyone alive in the after end of the submarine. This brought back the sad but not surprising word that all was flooded and no signs of life. Thus the rescue operations were competed, with 33 lives saved and 26 lost.
On the 25th orders were received from the Navy Department to salvage the wreck.
After one or two exploratory dives it was clearly indicated that we had little chance of success unless we used helium.
At the Experimental Diving Unit we had found that the ill effects of nitrogen under high pressure were almost entirely eliminated when using helium oxygen mixture as a substitute. We had spent nearly two years developing the proper decompression procedure following exposures with helium. Unfortunately some writers had created the impression that very little, if any, decompression is required when using helium. I have found in experimental work that most failures are caused by disregarding the simple laws of physics. Here was an example. Helium, nitrogen, argon or any other non-reacting gas that might be used as a dilutent or carrier in respiration, goes into the blood in simple solution by way of the lungs. As pressure is applied this gas is distributed throughout the body and enters the various tissues, water, fat etc. The quantity of gas that enters depends on the rate of blood supply. The tissues with great blood supply such as the brain, kidney, liver, stomach are fast tissues while those with a meager supply such as fat, joints, bones, etc. are called slow tissues. Naturally given time enough all tissues approach a condition of full saturation for the given pressure. It follows that when the pressure is released the non-reacting gas must be given an opportunity to come off and if insufficient time is taken, those parts known as slow tissues will be the first to give trouble by the gas forming as bubbles. While gas does move from one part of the body to another by direct diffusion as well as by the blood stream, and the rate of diffusion varies with various gasses, it can be clearly seen that all gasses must require decompression.
The theory of handling helium had been worked out, but the equipment for handling it was not quite ready when we were called to this job. That is the reason that helium was not used immediately. However, we started in, within a few days, to use the helium and thence forth used it exclusively when working at great depths. Knowing that 2.5 atmospheres of oxygen is safe to breath, the percentage of oxygen in the helium mixtures was calculated to give slightly less than this amount, and was roughly 28%. Since the gas that goes into solution in the blood varies directly as the percentage present in the lungs, it is advantageous to use as low a percentage of helium and as high a percentage of oxygen as is possible, but keeping the oxygen tension below 2.5 atmospheres.
In order to conserve helium which costs the government about one cent per cubic foot we devised a means of recirculating the gas in the helmet, through a CO2 absorbent, using a small gas supply as the driving agent, by admitting it through a venturi tube. By this means the oxygen supply was adequate in the driving gas and CO2 was kept at its proper level. This apparatus was not quite satisfactory at first but by making daily corrections and with the assistance of Mr. Philip Drinker and his friends we finally obtained satisfactory performance, and used the helium.
The minds of the divers were clear and they were so much more efficient when breathing helium that all divers were quickly converted to helium users by choice. As regards to this mental effect I feel sure that there is a definite relation between the molecular weight of the carrier gas to the mental effect. For instance the ratio of molecular weights of helium to nitrogen is as 4 is to 28, and the consensus of opinion of the divers as to feeling of depth seems to verify this. As a further study of the effect we used argon, molecular weight 40 as a carrier gas and found the effects on the minds to be similar to nitrogen, but proportionally worse. At ten atmospheres, I myself, was able to endure breathing a mixture of argon and oxygen, but a few moments. At atmospheric pressure the argon was not unlike air. If hydrogen were not so dangerous as an explosive it might make the ideal carrier gas. It may be used in the future for very great depths where the percentage of oxygen required would be very low.
The greatest single development produced on this job was the decompression system. Divers were brought by stages, calculated to be safe, to 50 feet. From this depth they were brought quickly to the surface, undressed and placed in a pressure tank within five minutes after surfacing. There he was fitted with a mask and given pure oxygen for a time sufficient to remove all of the excess gas from his body. 50 feet of salt water is equivalent to 1-1/2 atmospheres of pressure which added to the atmospheric pressure gives us 2-1/2 absolute. At this pressure the blood stream can handle in physical solution just about the amount of oxygen that is required by the body. Thus the blood stream as transportation is free to carry the greatest amount of the helium away to the lungs. Since the solubility of a gas in a liquid varies as the pressure, at a pressure of less than 2-1/2 atmospheres, the carrying capacity of the blood would be reduced, hence it would take longer to remove the gas.
Since at pressures substantially greater than 2-1/2 atmospheres man develops serious symptoms, commonly and I believe erroneously, called oxygen poisoning, we do not desire to use higher pressures. It is my own opinion that when the oxygen tension is increased beyond 2-1/2 atmospheres, the carbon dioxide removal is interferred with, for the reason that the oxygen in the hemoglobin is not reduced and the hemoglobin is unable to function as a chemical carrier of carbon dioxide. The removal of carbon dioxide by physical solution alone is insufficient. If this theory were correct we would expect to find the venous blood stream so crowded with CO2 in physical solution that the removal of helium or other carrier gases would be interferred with. This is, in fact, exactly what we did find. The amount of helium or nitrogen given off when breathing oxygen, following a measured exposure, reached a maximum at 2.5 atmospheres and then fell off rapidly as the oxygen tension was increased. The symptoms developed by breathing excess oxygen were found by Dr. R.A. Behnke to disappear very rapidly when the pressure was released and to leave no after effects. This gives further evidence that the symptoms are caused by excess carbon dioxide and not a "poison." Were were little concerned over the possibility of our divers developing symptons from breathing excess oxygen.
An interesting problem arose when using helium which was easily explained once we saw the light. Divers suffered much more from cold water, than from breathing air. The answer was that the specific heat of helium is greater than nitrogen and body heat was lost through radiation from the body. The development of electrically heated clothing solved this one. Resistance wire, wrapped in glass thread woven into glass cloth to reduce the fire hazard, was made up into panels. These were inserted between layers of wool. Electricity supplied by storage batteries furnished as much heat as was necessary.
Should the wreck of the Squalus have been brought from 240 feet to the surface rapidly, the change in pressure would have been about 107 pounds per square inch. Compartment hatches, ventilation valves and tanks cannot withstand such pressures inside. Consequently it was impossible to raise the hull in a single lift. In order to control the lift it was necessary to attach pontoons at each end of the hull, with wires or chains long enough so that short controlled lifts could be made. For instance the first lift of 80 feet was made by setting pontoons 80 feet from the surface and using them to check the rise of the hull above that point. Then when she hung on the pontoons 80 feet off the bottom we towed her into shallower water. That is in general how the lifts were made.
Permanent pad eyes or chains are not carried on submarines for sound technical reasons. It was, therefore, necessary to get wires and then chains under the hull at each end. Forward this was easy for the bow was up high enough to allow us to drag a wire under. But aft it was different. The stern was buried 18 feet into hard blue clay. To have tunneled under by usual methods at that depth was unthinkable.
We developed a tunneling lance. It was made up of 7 sections of pipe tapered from 1-1/4" diameter up to 2-1/2". Assembled, the whole lance was curved to the shape of the hull at the point at which we desired to go under. This point was at the shafts and we desired the chanins to be placed between the hull and the propeller shafts so that they would be held from slipping forward or aft by the propeller struts. On the entering end of the smallest section of pipe, a minature nozzle was attached. This nozzle had an opening for a stream of water on the forward end and anumber of smaller holes leading aft at an angle for water to flow back, thus to counter balance the forces of water, a hose was attached to the trainling end of the section of pipe. This was lowered down to a diver and he pointed it over the side. We turned on the water and the pressure tunneled a hole next to the hull down toward the keel. As each section disappeared over the side the hose was disconnected and a new section of pipe lowered to the divers to be attached to the end sticking out of the mud. When it was estimated that enough of the lance was under the hull, the water was turned off and air pressure was turned on. On the oposite side of the deck, in almost exactly the desired position, the bubbles were seen to be coming up. A wire snake was then run through the lance and the end was recovered on the other side. This was done on the 21st of June, 27 days after work began. At the end of 50 days work, connecting hoses, rigging pontoons, attaching bow and stern towing cables, the first lift was attempted. We raised the stern successfully then the bow. The bow came up like a mad tornado, out of control. Pontoons were smashed, hoses, cut and I might add, hearts were broken. It was the 13th of the month, July. Exactly 20 days of mopping up was required before we could again rig for another try. The second try was successful.
The hull was raised about 70 feet from the bottom and towed into shallower water on 12 August. We all felt very much encouraged because it was the end of our very deep diving and we knew that the system would work. 248 dives were made to the bottom without a serious casualty. But two cases of bends were developed and both of these could definitely be traced to the divers' coming up too rapidly. One of the cases would have been serious but for the prompt and correct treatment administered by Dr. O.D. Yarbrough. Squire, who had been trying to dig a hole in the mud with a tunneling hose, overworked, lost consciousness and blew up. His suit inflated and he came all the way to the surface. Quick and efficient handling by the dressing crew soon had him on board where his helmet, belt and shoes were removed and he was carried into the recompression chamber, still unconscious. The pressure was put on and built up rapidly to 200 pounds before Squire showed signs of recovery. When he did recover consciousness he was in great pain and raved and threshed [thrashed] about like a wild man. After about half an hour at that pressure he became normal and the long process of treatment begun. He was kept in the chamber for 16 hours and when he finally emerged the following morning he was little sore but otherwise fully recovered.
The other case was that of Crosby. After a routine dive Crosby came to his first stop at 90 feet. In order to help the tenders he lightened his weight by inflating his suit, good procedure when breathing air but dangerous when using helium, because of the rapid diffusion of the gas into the blood stream keeps it super-saturated and too rapid ascent might start bubbles in the blood vessels. Crosby complained of pains in his stomach at the 90 foot level. Lt. Wheland, one of my assistants, was supervising the dive and watched Crosby closely. He appeared to recover and was given normal decompression. Later in the evening Crosby developed symptoms of a serious nature. He was returned to the chamber and given treatment. He responded to the treatment and recovered completely.
These were the only cases of the bends in the entire job with a total of 628 dives. This is a record of which we are very proud.
Source: Biographical files, Operational Archives, Naval Historical Center.