It is, if you keep your mouth shut.
Always thought that was the #1 rule if you find anything of value, be it a sunken treasure ship or an unmarked paper bag full of money.
As for "investment opportunities" in sunken treasure . . . I'm reminded of the old Mel Brooks movie
The Producers, in which a couple of guys devise a scam that involves selling 50% shares in a Broadway play to dozens of investors, figuring that if the play flops, they could just keep the investments and not have to pay any profits. So they deliberately tried to make a play - a musical, actually - that would fail. (Didn't work out quite the way they wanted . . .
)