The Dive Boat is an aluminum hull landing craft built in 1968.  This boat design, called the LCM 8 (or sometimes just Mike 8), was 74 feet in length, and used for landing heavy tanks.  However, during the 1970s, the Navy converted 4 LCM 8s, including the one above, into dive boats.

This particular Dive Boat was assigned to the DSU, or Deep Submergence Unit.  Working in San Diego, California, it was designed for use as a rescue, salvage, or training unit.  The hydraulic arm on the stern could lower hard hat divers into the water, or pick up salvaged gear.  The Dive Boat also became the back up decompression chamber for a submarine in San Diego.