 Supermarine had tested this arrangement in the Type 322 and its capability was demonstrated when test pilot Mike Lithgow flew a Seagull at only .In July 1950, a Seagull, flown by Les Colquhoun competing in the Air League Cup Race gained the air-speed record for amphibian aircraft over a course, by flying at an average speed of .The hull was a normal frame and longeron design with chines.