Dermot Walsh as Guy Thornton

Hazel Court as Margaret Thornton

Joss Ambler as Yacht Port Manager

Hugh Burden as Dr. Fawcett

Mignon O'Doherty as Mrs. Manley

Hugh Latimer as Peter

Joan Carol as Mrs. Martineau

John Robinson as Prof. Martineau / Mansel

Joss Ackland as Ron, 2nd Fisherman

John King-Kelly as Sid, 3rd Fisherman

Laidman Browne as Coroner

Meadows White as Mr. Leech, Surveyor

Patricia Owens as Party Girl (Joyce)

Melissa Stribling as Party Girl (Vera)

Ian Carmichael as Bernard

Geoffrey Dunn as Strange Passenger

Pat McGrath as Bert, 1st Fisherman