Naval History and Heritage Command

A Navy ship's deck log is a daily chronology of certain events for administrative and legal purposes. Preparation of logs is governed by the current edition of Office of the Chief of Naval Operations Instruction 3100.7 (OPNAVINST 3100.7) series. A deck log identifies a ship's location and movements daily. If the ship is underway, its latitude and longitude are to be entered three times each day in blocks provided for the purpose. Deck logs are not narratives, and do not describe or explain a ship's operations.  (Visit our policy page for information on accessing and researching deck logs.)  

Information That May Be in a Deck Log

• Absentees 
• Accidents [material] 
• Accidents/Injuries [personnel] 
• Actions [combat] 
• Appearances of Sea/Atmosphere/Unusual Objects 
• Arrests/Suspensions 
• Arrival/Departure of Commanding Officer 
• Bearings [navigational] 
• Cable/Anchor Chain Strain 
• Collisions/Groundings 
• Courts-Martial/Captain's Masts 
• Deaths 
• Honors/Ceremonies/Visits 
• Incidents at Sea 
• Inspections 
• Meteorological Phenomena 
• Movement Orders 
• Movements [getting underway; course, speed changes; mooring, anchoring] 
• Passengers 
• Prisoners [crew members captured by hostile forces] 
• Propulsion Plant Status changes 
• Ship's Behavior [under different weather/sea conditions] 
• Sightings [other ships; landfall; dangers to navigation] 
• Soundings [depth of water] 
• Speed Changes 
• Tactical Formation 
• Time of Evolutions/Exercises/Other Services Performed 

Information Not Likely to Be in a Deck Log

• Individual Names: Deck logs rarely mention an individual’s name. Instances where a name is mentioned in the deck log include Captain’s Mast, arrival and departure of the Commanding Officer of the ship or VIPs, and major accident or death of an individual. The deck log will not provide information regarding specific treatment given to an accident victim. 
• Medical Treatment: Deck logs do not record medical treatment of injuries or other medical matters, such as visits to sick bay or injuries received off the ship. Medical records are sent to the National Personnel Records Center, St. Louis, Mo.
• Events Occurring Elsewhere: A deck log records events taking place on board the ship or, if pertinent, in its immediate vicinity. It does not include events taking place elsewhere, even if it involves crew members who are on liberty or detached duty.
• Arrivals or Departures: Deck logs may or may not indicate the arrival or departure of individual boats or aircraft. They do not list passenger names on these boats or aircraft. The only exception to this may be if that individual is a VIP. Deck logs generally do not log the routine arrival or departure of individuals going ashore. 
• Diary Material/”Captain’s Log”: A deck log does not record day-to-day work assignments of individual crew members.
• Shipyard Work: When a ship is being overhauled at a shipyard, the deck log records the ship's presence at the shipyard, but does not identify the work being done or the materials being used. These logs do not record day-to-day work assignments of individual crew members. A deck log records events taking place on board the individual ship or, if pertinent, in its immediate vicinity. It does not include events taking place elsewhere, such as the activities of crew members on detached duty.

Format of Deck Logs

Deck logs are bulky documents. Prior to the 1980s, logs were kept on oversized (10 by 15 inches) paper, a typical log consisting of four or more pages per day. In the 1980s, in keeping with a Congressional mandate to standardize on 8.5 by 11 inch paper, deck logs began to be written, by hand, on pages of that size. This greatly increased the page count; single months' logs from recent years run to as many as 300 or 400 pages for an aircraft carrier (up to 200 pages for a destroyer). Under the old format, a ship's deck log might run 120 pages or more per month, or over 1200 pages per year. Under the new format, logs can run from 100 to 400 pages per month or, say, from 1,200 to several thousand pages per year.

Most deck logs from 1979 to about 1993 are on microfiche, and the original paper copy for this timeframe was normally destroyed when the deck logs were microfiched. Deck logs for the post-1993 timeframe are in the original paper form.

Ships that Submit Deck Logs

Only deck logs from commissioned Navy ships are permanently retained by the Naval History and Heritage Command and the National Archives. A ship "in commission" is a Navy command in her own right; she has her own administrative identity, and originates records in her own name. Nearly all service craft are classified as "in service" rather than "in commission." They do not have their own administrative identity but are, in effect, floating vehicles operated by a parent command. Self-propelled service craft apparently keep a log of their movements for their parent command's administrative and legal purposes, but these are not sent to the Naval History and Heritage Command and do not go into any permanent file.

In Service/MSC/MSTS Ships: Navy-owned ships operated by the Military Sealift Command (MSC), formerly the Military Sea Transportation Service (MSTS), are classified as "in service" and manned by civilian crews. Inquiries concerning MSC ships' logs should be directed to Commander, Military Sealift Command. The identifying hull name of Military Sealift Command ships are prefixed by "T" followed by a hyphen and then the number. For example, the commissioned oiler USS Platte is identified as (AO-186), while the MSC-operated oiler USNS Pecos is identified as (T-AO-197).

Merchant Ships: There is no central repository for deck logs from merchant ships. Deck logs were traditionally considered to be the property of the ship owners to be held or disposed of according to their own recordkeeping practices. After World War II, the deck and engineering logbooks of vessels operated by the War Shipping Administration were turned over to that agency by the ship owners, and were later destroyed by the Maritime Administration in the 1970s on the grounds that they were voluminous, costly to house and service, and very seldom used for research.

The National Archives and Records Administration (NARA) has custody of the official logbooks, which were issued to American registered merchant vessels at the beginning of each voyage, and were turned in to the United States Commissioner at the port where each vessel ended its voyage. In these logbooks, masters were required to keep information related to the health and welfare of crew members. These logbooks are not records of ships' operations, but are essentially records of personnel matters, collisions, emergency drills, and information on ships' watertight integrity. The official logbooks from U.S.-registered merchant ships are held by the NARA Regional Archives closest to the U. S. port where each voyage ended. This port can be determined from the movement report cards which are part of the Tenth Fleet collection held by the Modern Military Branch of NARA. The movement report cards list the ports of call, the dates of arrival and departure, and the convoy designation, if the ship sailed in a convoy.

The Tenth Fleet records also contain the loss and damage reports for merchant ships, and folders about the individual convoys. Other collections held by the Textual Reference Branch of NARA, College Park, Md., that are useful for understanding merchant ship movement and operations include the Naval Armed Guard reports from each voyage and the Bureau of Naval Personnel's Naval Armed Guard Casualty reports. For the period of World War II, Naval Armed Guard detachments were assigned to U.S.-flag merchant ships, Army transports, and even some foreign-flag merchantmen.