For anyone interested in Genealogy I see that the "Find my Past" web site now has records of Merchant Navy Seaman online. This is a commercial site and although you can do an initial search to see the list of what is available you need to subscribe to see the detailed records. I have used this site in the past when researching family information so I was interested to find they have added these records.
Merchant Navy Seamen 1835-1857: records of individual seamen that the central government created to monitor a potential reserve of sailors for the Royal Navy
Merchant Navy Seamen 1918-1941: records of index cards that the Registrar General of Shipping and Seaman used between the two world wars to produce a centralised index to merchant seamen serving on British merchant navy vessels
https://search.findmypast.co.uk/search-world-records-in-military-armed-forces-and-conflict
