Again, Tony D. will advise us, but I believe that even the captains of British registered ships no longer have the power to conduct a marriage that will be both legal and recognised in the UK, they used to, but I don't think they do any more.
Having been brought up in Hampshire and spent many a lovely day down on the Solent watching the ships pass out from and into Southampton Water, when merchant shipping was the major form of transport in the world, I got a yearning to travel, it never left.