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.

Tense moments mix with comedy when three students capture the Endeavour and, thinking the crew are spies, plan to hand them over to the police.

Old Harry tells Steve Gabo about two million dollars of gold coin carried on a plane lost during World War 2, which he has been trying to locate for years. The Minus Five team begin a search and find more than they bargained for - two skeletons, and two armed men who could be murderers, but who are in fact Commonwealth Police.

The Endeavour puts into a slipway in Townsville for inspection and maintenance, and the crew welcomes Diana Parker, the charming new operator for the Minus Five equipment. But there are shocks in store for all as Diana is discovered to be an impostor, and one of the diving crew narrowly escapes death.

Exploring an underwater oil field near the Great Barrier Reef, the mini-submarine crew strikes new danger - an ear-splitting, high-frequency sound that kills fish, and even disables the Minus Five electronic equipment.

The Minus Five team become involved in political intrigue when a defector from a Russian ship asks them for political asylum in Australia. Steve Gabo takes his side, until he learns the Russian is not a refugee, but a thief.

The Endeavour runs before Cyclone Ada, which devastates tourist resorts on the Great Barrier Reef and towns on the North Queensland coast. After the disaster, the Minus Five team return to the area to search for survivors, and play an important role in rescue work.

The Endeavour crew are assigned to search for a fishing launch sunk during the cyclone. They plunge into a murder mystery when in the cabin they find a body with a knife in his back.

A beautiful young girl from Thursday Island stows away on the Endeavour, claiming Jack Meurauki has promised to marry her. Hiding the girl from the Captain proves a major problem.

Minus Five picks up uranium readings which appear and disappear. A trawler hauls in a catch of fish which could be radioactive, but a more important 'catch' is contested with spear guns under the ship as the Endeavour crew stumble upon uranium smugglers.

The Endeavour is assigned by the government to chart unknown channels in the Barrier Reef. A man once badly mauled by a white pointer shark seeks revenge in the shark's breeding ground and endangers the lives of the Minus Five divers.

The Minus Five team is commissioned by the Royal Australian Navy to locate and chart a mine field off the Barrier Reef. During the trip, Captain Ted King risks his life to rescue one of his crew trapped in the mine field, while mines are breaking loose from the rusted cables and menacing the ship.

The Endeavour's attractive new scientist learns a bitter lesson in security when she innocently arranges passage to Townsville for a colleague. Customs officer Morgan and the Minus Five team are held at gunpoint by the passenger who demands the surrender of counterfeit money plates which have been discovered attached to the ship's hull.

A wreck with a cargo of whisky hangs precariously on a ledge on the Reef. A puritan Scotsman plans to destroy the cargo, and a drunken beachcomber warns the Minus Five team, who are working to retrieve a new navigational aid from the wreck. The navigational aid must be assessed, for if it is defective it could endanger the other five ships it has been issued to, but their work is hampered by the old Scotsman who is determined to destroy the whisky before it can cause any evil.

A mad scientist, intent on preserving the Barrier Reef from exploitation, plants explosives aboard the Endeavour as the crew wait to welcome the Royal Britannia during the Royal Visit to Townsville.

A Japanese submarine sunk during World War 2; a Shinto burial service; and the unusual interest displayed by a Member of Parliament plunge the Minus Five team into a new mystery on the Barrier Reef.

A strange illness threatens the life of three people on the Great Barrier Reef when an old scientist loses control of dangerous research into the effects of radiation on the cycle of marine life.

A wealthy fisherman hunts for a world record size shark, and baits an area with bloody meat. One of the Minus Five divers becomes trapped by a thrashing shark pack attracted by the bait.

The owner of an illegal fishing fleet is desperate when the Minus Five team find a strange tripod on the sea bed which is his early warning system. He sends out a bogus distress signal to lure the Endeavour away from the area.

The idea of icebergs in the tropical waters of the Barrier Reef at first amuses the Minus Five team, but the situation becomes grim when the icebergs prove to be real and a threat to shipping. Captain Ted King asks the inventor of the icebergs on board the Endeavour to join the team.

A deadly, radioactive 16½ inch cylinder, released into the sea near the Great Barrier Reef from the crippled spacecraft Apollo 13, must be recovered and contained before the whole area becomes a graveyard. The assignment is given to the Minus Five team.

A bizarre attempted murder by the Mafia can only be prevented by a marine biologist and the Minus Five team working together. They must catch a deadly stone fish alive so that an antidote can then be made to save the dying man.

An ageing sea captain who was the original skipper of the Endeavour determines to scuttle the ship so they can die together. Alone with him on the ship, Tracey Deane tries to change his mind.

One of the Minus Five team acts as bait to catch a company official selling classified information about a newly discovered nickel field on the Barrier Reef.

The Minus Five team find an unconscious diver in the water and another on the sea bed. Attempting a rescue, one of the team gets nitrogen narcosis and tries to give a shark boxing lessons.

When the roof of a cave below the Great Barrier Reef collapses and traps one of the Minus Five divers, the others have to work against time to rescue him.

A live missile embedded in the coral reef makes a dangerous proving ground for a celebrated Royal Australian Navy diver who has lost his nerve.

A monster turtle and a blonde diver girl form a strange alliance to frustrate the Minus Five team's latest assignment.

Foreign voices are heard by Kip over the radio as he searches below the Endeavour for one of his tools. The Minus Five team are challenged by strange divers who accuse them of spying.

A desk-type security agent involves the Minus Five team in a dangerous duel with jet-boats when two men are discovered tapping an undersea cable and selling information to a foreign power.

The Minus Five team play cops and robbers with a pearl smuggler, and one of the team becomes trapped in an underwater cave.

The Minus Five team become involved in a lover's quarrel, which quickly turns very serious when the girl involved is trapped in a cage on the sea bed, and all evidence points to attempted murder.

The Minus Five team need all their skill to locate and rescue Kip Young, who has been overcome by the energy force of a sonic fence which was laid to warn submarines approaching the Great Barrier Reef. (Final episode of the series.)