The vehicle you see is a Marine Corps amtrac (amphibious tractor) -- to use WW2, Korea, and Veitnam vernacular, or LVT-7P (landing vehicle tracked, model 7, personnel).  In 1984, the Marines redesignated them as AAV"s (armored amphibious vehicles) from the older LVT designation. 

 

This vehicle is the AAV-7A1.  It is powered by a Cummins VT-400 diesel engine and propelled by two water jet pumps at the back.  It is much faster and less suseptable to swamping than its predecessor, the LVT-5P.  The LVT-5P came out after the Korean War and was used extensively in Vietnam.  It was gasoline powered and looked like a box with tracks.  The LVT-5P carried all its fuel in the belly and was powered by its tracks when swimming.  In Vietnam the Marines found that the LVT's fuel location was very dangerous.  If the amtrac hit a mine in the road, the explosion usually set the fuel tank on fire.  Marines rode on top of the vehicle (exposed to small arms fire) instead of inside the protective armor.  It was replaced by the LVT-7P in 1972.

 

This particular AAV-7A1 is part of a training batallion.  The amber light atop the vehicle is use when the amtracs are doing road marches while ashore to warn civilian vehicles to stay clear.  The commander's cupola on the right side of the vehicle was upgraded during a SLEP (service life extension program) beginning in 1982 that made many improvements including new engines and transmissions to the original AAV-7P.  Vehicles modified under SLEP (designated AAV-7A1) received a fuel burning smoke discharger that allows the vehicle to lay its own smoke screen to confuse enemy observers.  The new cupola adds eight smoke dischargers (for screening the vehicle), a .50 AN/M2 HB Browning machine gun and a Mk 19 Mod 3 40mm automatic grenade launcher -- all enclosed in a fully stabilized and armored turret made by Cadillac Gage Corporation. 

 

The driver's cupola (with vision blocks) is on the left side of the hull.  Unlike the earlier LVT-5P that had its ramp in the front, the AAV-7P has combination door and ramp in the back.  The top deck of the vehicle has a set of hinged doors to allow the Marine rifle squad in side to fight without dismounting.  Notice the brackets on the sides of the hull.  These brackets are for attachment of Enhanced Applique Armor Kits (EAAK).  These kits give the vehicle more protection against shaped charge anti-tank projectiles, such as the Russian RPG-7V.  The AAV-7A1 carries a crew of three and 22 combat Marines.

 

The AAV-7 has other versions besides the one pictured.  There is a command version with extra communications equipment and a recovery version with a crane.  The recovery version is used to move disabled amtracs and do engine changes or other maintenance functions in the field.  A modification of the standard AAV-7 is the armored engineering vehicle with the Mk 154 linear mine clearing charge.  This is a rocket-thrown length of hose filled with C4 plastic explosive.  In use, it is fired over the mine field and then detonated.  The resulting blast either destroys or causes sympathetic detonation of mines to blast a path for infantry and armor.  The Marines plan to replace the AAV-7 series vehicles with the Expeditionary Fighting Vehicle (EFV) in 2015.

 

Current users of the AAV-7 are: (1) the USMC with 1311 of all types; (2) Argentine Marine Corps with 21 AAV-7P; (3) Brazilian Marine Corps with 25 of all types; (4) Cambodian Navy with 63 of all types; (5) Italian Army with 35 of all types; (6) Republic of Korea Marine Corps with 162 of all types; (7) Spanish Marine Corps with 16; (8) Royal Thai Marine Corps with 24 of all types; and Venezuelan Navy with 11 of all types.

MSN has dropped out the photos of the AAV-7A1.  So here are some recent photos.