sentence: as well as saunders-roe and vickers ( which combined in 1966 to form the british hovercraft corporation ( bhc ) ) , other commercial craft were developed during the 1960s in the uk by cushioncraft ( part of the britten-norman group ) and hovermarine based at woolston ( the latter being 'sidewall hovercraft ' , where the sides of the hull projected down into the water to trap the cushion of air with ` normal ' hovercraft skirts at the bow and stern ) .