Underwater Island

[Landshark]

So I've been contemplating the island being underwater in the season premiere "ALT". I was wracking my brain trying to think about who or what caused the island to now be underwater. Then it hit me. Maybe a good place to start is figuring out what can cause an island in "real life", to end up submerged on the ocean floor. Also, everything on the Island like the houses in Dharmaville, and the foot of the statue are intact, which narrows our possible answers. For example, I think the structures being intact point to it NOT being Jughead detonating that sinks the island.

The only thing I could think of, off the top of my head, was a rising sea level. I don't see how this could be our answer, as I'm sure it will be a lot more fantastic than that. Obviously this is LOST, so they can be pretty liberal in the way they answer this.

Anyone have any other "scientific" explanations for an island, and all of it's structures intact, to have sunk to the ocean floor?