 Nine of these boats were ordered for use by the RAF Marine service by 1932.In 1935, larger boats were also ordered; these were fitted with wireless systems that allowed the launch to communicate with the Station and the search aircraft, allowing for an efficient system of contact to be maintained.The Type Two 63 ft HSL was designed in 1937 by Hubert Scott-Paine; 63 foot long and known as the "Whaleback" from the distinctive curve to its deck.