Barrier Reef

A high ranking Government official makes a secret visit to the Endeavour to determine whether General Trust Corporation may use it's Minus Five equipment to commercial advantage without affecting the natural heritage of the Great Barrier Reef. The project is placed in jeopardy when, riding in the mini-submarine, he nearly loses his life. Dr. Paul Hanna, of the Government Science Council, joins the team on board the Endeavour.

A Spaniard tricks the Minus Five team into using their equipment to locate a sunken galleon which, he says, carried a fortune in gold. His real reason is to prove a Spaniard discovered the Australian coast before Captain Cook.

An industrial spy gets aboard the Endeavour to photograph the top secret equipment, but he turns out to be not such a bad bloke when he realises his methods endanger Captain King's life.

The Minus Five team discover a murdered man in Barrier Reef waters, and he is buried on a small, lonely island. He is to be exhumed by the police, but when Sgt. Davies goes to the grave the body is missing, and the Minus Five team land in a strange network of intrigue.

Two nuns ask the Minus Five team to help them recover a sacred chalice lost in a wreck off the Great Barrier Reef, but Captain Ted King reluctantly declines assistance as the Endeavour is under orders for another assignment. The nuns risk their lives when they decide to attempt the salvage job themselves.

The Minus Five team has salvage rights to a vessel sunk off the Barrier Reef in the 1800's, but when they arrive they find divers down below. The gold disappears and it seems it has been stolen from under their noses. A cannon from the wreck and an old log book must be found before the mystery can be solved.