The Ford class seaward defence boats were built for the Royal Navy in the 1950s. They were designed to detect and attack hostile submarines, including midget submarines in inshore waters such as the approaches to large ports. They were powered by diesel engines and were planned to be armed with a single barreled Squid anti-submarine mortar. This special version of the Squid was a failure however, with the first Ford-class boat, HMS Shalford being fitted with a normal three-barreled Squid and the remaining vessels with a more conventional anti-submarine armament of depth-charges throwers. A single Bofors 40 mm gun completed the armament.