This is a WW-II vintage amphibious tracked vehicle in about 25' off Del Monte Beach. Presumably it set sail from Ft. Ord intending on invading Monterey. It's usually dived in conjunction with the Sailboat. It's easiest to do the Amtrack first, then swim NE to the sailboat (about 110' on bearing 40 magnetic ) Why the Amtrack first? Because the Sailboat is a bigger target and therefore easier navigation on the bottom. The Amtrack itself is pretty rusted, but you can still see pieces of the the tracks laying next to it. It's NOT a half-track which has tracks and front tires, but rather an Amtrack, which is all track and somewhat amphibious (well, this one wasn't ). Alternative spellings are amtrak, amphtrack , amptrack and combinations thereof.