ATC aka Tango Boat Vietnam

Armored Troop Carriers (ATC's) with mounted 30- and 50-caliber machine guns, Mk 19 rapid fire grenade launchers, and 20-millimeter cannons transported the Riverine Infantry throughout the delta. In the early part of the war this was principally troops of the 9th Infantry Division. Later Vietnamese Army and Marine troops took the fight to the enemy aboard the Tango boats. Those Tangos with added helo decks, ATC(H), also provided a means of landing helicopters for swift evacuation of the wounded. All Tango boats have the distinctive bow ramp.