Many naval vessels apart from aircraft carriers carried float planes, seaplanes or amphibians for reconnaissance and spotting. They were catapult-launched and landed on the sea alongside for recovery by crane. Additionally, the concept of submarine aircraft carriers was developed by multiple nations during the interwar period, and through until WW2 and beyond, wherein a submarine would launch a small number of floatplanes for offensive operations or artillery spotting, to be recovered by the submarine once the aircraft has landed. The first launch off a Royal Navy battlecruiser was from on 8 March 1918. Subsequently, many Royal Navy ships carried a catapult and from one to four aircraft; battleships or battlecruisers like carried four aircraft and carried two, while smaller warships like the cruiser carried one. The aircraft carried were the Fairey Seafox or Supermarine Walrus. Some like did not use a catapult, and the aircraft was lowered onto the sea for takeoff. Some had their aircraft and catapult removed during World War II e.g. , or before ().