Observation seaplanes are military aircraft with flotation devices allowing them to land on and take off from water. Their primary purpose was to observe and report enemy movements or to spot the fall of shot from naval artillery, but some were armed with machineguns or bombs. Their military usefulness extended from World War I through World War II. They were typically single-engine machines with catapult-launch capability and a crew of one, two or three. Most were designed to be carried aboard warships, but they also operated from seashore harbors.