If you have no details of the ships that a seafarer sailed on, you will need to rely on indexes.
For the period from 1861 to 1913, there are millions of records of seafarers, but no central index of seafarers was made at the time. There is no single modern index anywhere, and probably never will be.
However, there is some hope - many indexes do exist as this page explains. Either scroll down or use the links.
Where data is available online, we provide a link to it. A (£) symbol means you will have to pay for the data.
Bear in mind that you only need to be lucky once, because the seafarers' records show the previous vessel they worked on so you can trace back their career from one voyage to the previous one. Also, if they were at sea for some years, records of an individual seafarer will appear on many documents, so the chances of finding at least one record is increased. Remember that seafarers could sign on to a ship from any port, so look in as many indexes as possible - you never know!
Several local archives have indexes of seamen from the crew lists and agreements they hold. The format varies - card indexes, printed, or as part of the catalogue. Some archives have indexes of masters and owners only. Unfortunately, many online indexes at archives work through catalogue systems such as CalmView that are best described as nomadic and user-hostile.
It's worth searching all of them because seafarers often sailed on ships registered in other parts of Britain, not just their own home port. The table below shows the archives which have at least partial indexes.
If the seafarer was (or might have been) a Master, Mate or Engineer, search at The National Archives (TNA) in the registers of certificates (BT 122 - BT 130 and BT 138), Lloyds Captains’ Register and Engineers’ certificates registers (BT 139 - BT 142). However, many officers did not have certificates.
As mentioned above, the original copies of Lloyd's Captain's Register are held at London Metropolitan Archives. The volumes have been indexed and some are available online.
If the seafarer died at sea, the death may be recorded in the registers and indexes now held at TNA and listed below:
TNA has an information page TNA information - BMD at sea setting out the details of the registers.
If the death is recorded, it may be possible to obtain a certificate of death from the General Register Office (GRO) - see below.
For seafarers on Scottish ships, ScotlandsPeople has an online index of deaths at sea. On their search page for deaths, select 'Marine register' as the district. You can purchase copies.
It appears that not all deaths at sea were reported to the Registrar General until the 1860s.
They were entered into registers similar (but not identical) to those now held at The National Archives (see above). TNA has an information page TNA information - BMD at sea setting out the details of the registers, both their own holdings and those at the GRO.
The indexes show the age at death and the ship's name (but not her official number) from 1875 onwards.
You can find out more about these records at Findmypast (£) and look up various indexes. There is a charge for viewing the index images.
Death certificates, which are copies of the register entries (and could therefore include details such as the ship's official number), can be obtained from the GRO by phone, post or online General Register Office Online Ordering
British censuses were taken every tenth year from 1801, but the names of individuals were only recorded from 1841. Crews of vessels were included from 1851 using special enumeration forms. Only ships which were in a British port on the night of the census were included, though from 1861 arrangements were made to include ships which were at sea in the home trade, Ships in a foreign port on that night were not enumerated.
The complete story is more complicated. Edward Higgs' guide to the census take four pages to describe it. (E Higgs, Making Sense of the Census Revisited, London, Institute of Historical Research, 2005, ISBN: 300100396X, pp.48-52).
If you have an image of a census return for the ship, be sure to look for the ship's official number, which will help in finding other records, particularly crew lists. This information may be on a separate page ahead of the main image. Unfortunately, some Findmypast images do not include this page.
The ship's port of registry is also useful information (ie her "Port or place to which she belongs", not the port at which the enumeration was made).
For details of the census returns for ships from a historian's perspective, see Dr Valerie Burton's paper A floating population .