Carden-Lloyd amphibian tanks (A4E11) arrived in the Soviet Union in 1931. Engineers at Zavod Nr 37, directed by N. A. Astrov, developed several prototypes. It was called the "Morskoi 33" or "Malyi Tank 33" (T-33). It's performance in water wasn't acceptable and a new design appeared in 1932 called the T-41. It to turned out to be unacceptable and in 1933 another model was developed and it was the T-37. On August 11, 1933, it was accepted by the Red Army after trials. Another group of designers led by N. N. Koziryev also designed a variant, the T-37A.
It had the turret mounted on the right side and the tracks were improved. A ship's propeller was added that allowed for the vehicle to move backwards as well as forwards in the water. Late models had a cupola for the commander.
The T-37 Type A had a 7.62 mm DT 1929 MG installed. It had a range of 800 meters and could fire 600 rounds per minute. The velocity of the bullets was 840 m/sec.
There were two pontoons located above the tracks. Balsa wood floats encased in sheet metal were added to the T-37 to make it more buoyant.
The engine used in the T-37 was the GAZ AA.