Hi BVI
Unfortunately the Treasure Trove act only applies on land.
Recreational Underwater Archaeology is all but dead nowadays, as in situ-preservation having to be the first option has removed any incentive to search for and run a project ( nobody will spend all their hard earned cash year in year out just to survey a site then monitor its slow destruction).
New draconian environmental legislation (Marine Management Organisation) has made the use of dredges, airlifts, lift bags over 25kg etc, a licensable activity that cost both time and money, so that has put paid to most small groups running active archaeological projects.
The state funded sector has so little cash they are also doing next to nothing.
Its a very sad situation for a Maritime Nation that for so many years was at the forefront of a Underwater Archaeology.
It makes my heart bleed to see wrecks like the Sterling Castle, Roswijk, Colossus, etc, etc, just eroding, corroding and being swept away due to the flawed ethical thinking of a few who don't have the interest, motivation or money to do it themselves.
Still the trashing and looting sites is thriving as people know that if the grown-ups are not interested in recovering the stuff they cant be interested in having the knowledge controlled recovery would have brought.
Sad old times. Stay in the BVI the UK had f*ckef itself on so many levels from uncontrolled immigration to unnecessary legislation.