That’s only effective until the saltwater eats away at all of the seals, at which point it’s free again. Ancient vaults containing artifacts of fell power and their incumbent curses comprise one of the most popular adventure story archetypes. The point is, it’s only gone until someone stumbles across it, and now it’s _un_gone, and worse, the hapless stumbler has no idea what’s going on.
That’s only effective until the saltwater eats away at all of the seals, at which point it’s free again. Ancient vaults containing artifacts of fell power and their incumbent curses comprise one of the most popular adventure story archetypes. The point is, it’s only gone until someone stumbles across it, and now it’s _un_gone, and worse, the hapless stumbler has no idea what’s going on.
The bottom of the ocean is pretty inaccessible even if the container rusts away.
But that doesn’t stop the thing from getting out when the seal corrodes away…
If the container itself is flimsy enough to corrode away, escaping it is inevitable.