I think it'd look cool. however, it shouldn't be submerged, since you can't place a gold mine in water or on cliffs. I have one suggestion though, ADD CORAL! kindof like the entangled gold mine, but since it's near ater and naga are water units, coral makes sense. and, why not just leave them with slaves walking in and out? It's simple, and you don't have to make another building in the game.