Proyekta 1124: their standard armament was initially two turrets from T-28 or T-34 tanks, each mounting a 76.2 mm gun and Degtyaryov tank machine gun (DT), as well as two anti-aircraft machine guns – in some cases the rear turret was replaced with a Katyusha rocket-launcher
Proyekta 1125 (ru; zh): one T-28/T-34 turret with a 76.2 mm gun and DT, as well as four AA machine guns
S-40: one T-34 turret with a 76.2 mm gun and DT, as well as four AA machine guns
With crews of 10 to 20 personnel, riverine tanks displaced 26 to 48 tons, had armour 4–14 mm thick, and were 23 to 25 metres long. They saw significant action in the Baltic and Black Seas.
Known for use in rivers and bays and having a speed comparable to that of a tank I can see this being great for base defence against tanks and lvts or a support role in a base take.
http://wio.ru/fleet/ww2armorb.htm