Complex sentence: Ramped Cargo Lighters were used by the commando unit, Popski's Private Army (the crews were Royal Engineers) in the Venice escapade and for transporting Popski's Private Army around the marshes, canals, and flooded areas in Northern Italy.
Split into simpler sentences: Ramped Cargo Lighters were used by the commando unit, Popski's Private Army (PPA). The crews, Royal Engineers, sailed the PPK into Venice and transported them around the marshes, canals, and flooded areas in Northern Italy.