The Soviet 'ASU-57P' Built in the 1950's this prototype airborne Assault Gun would have the additional benefit of being amphibious.

The vehicle would not see mass production and only have 5 prototypes built.

The main weapon is a 57mm CH-51P gun.
The ASU-57P would be powered by a 55hp M-20E4 engine and had a top speed of 45km/h on land and ~8km/h in water.

@WheelsOfDefenseGlobal