He lives at the sea floor, and at the sea floor, the pressure from all the water above you is really high, obviously, he doesn't live in the deepest part of the ocean, and sponge Bob can withstand being at a location that's probably 1000-3000 feet below the surface, but if the sea level was higher than mountains, he would die. (It really doesn't matter how deep in the ocean he lives, he'd still die from the sea level increasing so drastically)
