The fact that this gent found her doesn't make her his property. I have no idea what Filipino law says about shipwrecks. The fact that she was a naval vessel complicates things. I don't know what possible claim Japan may have to the wreck. Or, for that matter, the governments to which Japan surrendered.
Confederate shipwrecks are the property of the U.S. government. So is the USS Arizona. The Musashi. As a Japanese warship lying in Philipino waters, is, I suspectt, a comlex legal case. I suppose there's a potential there for a bunch of lawyers to make a whole lot of money. Personally, I'll be happiest if they photograph the wreck, document it, and leave it in peace.
Youth, talent, hard work, and enthusiasm are no match for old age and treachery.