Inside, you’ll find the Alien Blaster along with a rusted key. Just in front of the bath tub should be an open wooden crate submerged beneath the water’s surface. There will also be a ramp with a bath tub at the end of it nearby.
As you draw closer to the eastern edge of the lake, you should notice the wreckage of a destroyed house sinking into a patch of water that has been separated from the larger lake.