The records of seamen who joined the Royal Navy between 1853 and 1923 can now be searched and downloaded from DocumentsOnline, The National Archives' digital records service.

The UK National Archives' site notes: 

While many of the records from the Registers of Seamen's Services (ADM 188) and the Continuous Service engagement books (ADM 139) have previously been digitised, we have only recently completed the collection by releasing the final batch of files (ADM 221 - 1027) online. This means that over 680,000 records on Royal Naval seaman are now available to search and download.

Many of the records reveal year and town of birth, names of ships served on and the period of time served in the Royal Navy. Even greater detail can be found in records from 1892 onwards, invaluable for those tracing their naval ancestors. Entries on occupation and physical appearance, such as hair and eye colour, height and tattoos can be found, and even notes made about 'character' and 'ability'.

The records are free to search, but there is a charge of £3.50 to download. The service records of Royal Marines and Royal Naval Officers are also available from DocumentsOnline.