The Merchant Navy are the unsung heroes of the First and Second World War. Merchant navy casualties were very high in both World War I and World War II. A War Office Report of 1922 entitled Statistics of the Military Effort of the British Empire During the Great War 1914-1920 listed British Merchant Navy losses at a figure of 14,661.
King George V bestowed the title ‘Merchant Navy’ upon the UK registered commercial seagoing ships and crew following their service in the First World War.
2nd World War Merchant Navy total casualties are recorded at a figure of 45,329. The Dover War Memorial Project confirm that a third of Merchant Navy seamen did not survive the 2nd World War. Those killed numbered 30,248, the missing numbered 4654, the wounded numbered 4707, prisoners of war were put a figure of 5720. There is a lot of information on the Dover War Memorial Project website.
Find My Past have digitised 570,000 records of Merchant Navy Crew lists for the period 1861-1913. This will include the records of the Ships Master or a deck hand. There are over 157,000 images of original documents. Here is the relevant search page:
In 2015 Ancestry released an extensive list of Indentured Merchant Navy Apprentices for the years 1824-1910. It contains the records of 340,000 apprentices including ports travelled to. By Law Merchant Ships were required to carry a certain number of apprentices. There’s an interesting record of a debate in Parliament in 1823 on the Merchant Vessels Apprenticeship Bill including the comment from a Mr Huskisson “One object of his bill would be to make the advantages equal in all merchant ships; and this he proposed to effect by a clause, that every merchant vessel in every trade should have an equal number of apprentices, in proportion to her tonnage. He also proposed to give to apprentices greater protection against impressment. At present those of 17 years of age were liable to be impressed after three years service. He proposed that apprentices should not be liable to be impressed under the age of 21.”
Here is the relevant page: