So the title basically explains what this is. It's a LARC (Lighter Amphibious Resupply Cargo) vehicle. It looks like a boat with wheels...because it is! Now, as interesting as this may be, the reason why I thought it was particularly peculiar was that it was parked out near Montauk, NY.
The only military base nearby is a Coast Guard station, and after giving them a quick call, they said that while they do work with the Army Corps of Engineers, they have not seen nor used this vehicle. After some research, apparently only the US Navy still uses these vehicles, servicing about 200 of the remaining 400 in the world. So, either they never removed the Army Corps of Engineers insignia, or whoever bought it from auction just likes the look.
So, while it is parked next to a cheap motel on the side of a highway, I kept wondering why it was there, so far from it's home I'm assuming is near NYC.
On a side note, this is one of the cooler military vehicles I've seen before. It can go about 30 MPH on land, and 7.5 knots on the water (8 MPH). It's also AWD and has a 375 HP turbo-diesel engine on board.
According to a commenter below, The Transporter, it appears that on the last photo the vehicle sports a US Navy registration number. So why does it still have US Army insignia on it? Furthermore, the stars on the hubcaps is not an official paint scheme according to said user. The last time I ever saw stars on military vehicles was from WWII. Plus, all records of this vehicle show it painted silver/white/grey, no green.