Fowler Challenger III amphibious tractor
Fowler Challenger III is a continuous track amphibious launch tractor, which was specifically designed for the Royal National Lifeboat Institution (RNLI), to launch and recover carriage mounted lifeboats, from beach-launched lifeboat stations. A total of 13 tractors were constructed over a seven-year period from 1953 to 1960.
Source: Wikipedia — Fowler Challenger III amphibious tractor (CC BY-SA 4.0)