If you have ancestors who were on British Merchant Ships, you can now have a look at the indexes to the Crew Lists from FindMyPast. For those of you who do not have a FindMyPast subscription, it will cost you 5 credits to view a single crew member and another 15 to view the crew list.
From these indexes, you will get enough information to search other respositories where the original documents can be found. Minimally, you will get the Official Vessel Number from the crew lists. You will need this number to access the original record. Most of the records are available at the Maritime History Archive. The records detail the employment of each member of the crew. This includes deck hands, stewards, maids, nurses and engine staff. These were updated every six months.