Just a thought, Keith - that records of deaths at sea from 1891 to date are held at the General Register & Record Office of Shipping and Seamen, Llantrisant Rd, Llandaff, Cardiff CF5 2YS. I don't know whether this applies only to the UK records, but it could be worth asking.
After the mid-1800s each vessel was given an official number on registration which was retained for the life of the vessel and not reused - these used to be found in the Mercantile Lists, but my information comes from the 1800s. The PRO culled their holdings to 10% after 1860, but the National Maritime Museum, Greenwich SE10 9NF holds some, including 1875, 1885, 1895 [then 1905].
The Maritime History Group, Memorial University, Newfoundland, Canada holds the remaining Lists [about 70%].
If you write to these places why not ask about Thomas Brew's fishing vessel 'Sea Spray' [1881 census], and George Thomas Brew's 1901 vessel "Britannia" as well as the 'Majestic'?
If the vessels were registered they will have had a port of registry, by number [e.g. Sydney was 207]. There was no index after 1856 to the seamen contained in these lists - information only by vessel.
Sue