Or a boat?
I have to do some research to see if it is a prototype. Can't be a any kind of boat due to the barrel would capsize it every time. There wasn't any info on the site where I found it.
OK, I found it. This is a Russian Prototype called the Object 279 circa 1957 only two were built and they are in a museum in Kubinka, near Moscow. Khruschev canceled these in favor of missile tanks www.thedonavon.com/archives/artillery
Looks more like a UFO than a tank to me.