Lost Mountain

This is it, you made it so deep underwater that there's possibly nothing but magma under you. You've been exploring for days, weeks, months and you finally found the Lost Mountain. But was it worth it? You're now stuck down here, with possibly an insanely huge pool of lava under you, constantly boiling, waiting for prey to fall in, there is no more marine life, you're the only one here and you will probably not get out of this alive.