Island of the Khoisan

Five people abandon a sinking cruise ship and are stranded on a desert island. Two adults, members of the ships staff, and three children, aged 19, 11 and 12 who were passengers, now separated from their families.
They set about building shelter and foraging for food. Whilst exploring the island, they discover small bay which is a much pleasanter area and move there. They happen upon a family of apes, a large male, two females and three babies. The young ones run to the people, wanting to play and have friendly romps, until the male calls them back.
They find a boat stranded on a beach. They sail the boat back to their new home in the bay.
On the north east of the island, four people who are also survivors from the shipwreck, been captured by strange species. When they try to free the captives they are attacked by the captors. They manage to escape from the captors and return to the bay. Finally, a British Navy vessel comes to their rescue and takes them home.