
In 2064, Captain Troy Tempest of the World Aquanaut Security Patrol and his crew explore the oceans in their combat submarine Stingray, encountering friendly and hostile undersea aliens.

Following the destruction of a WASP submarine, Troy and Phones are sent to investigate. They are soon captured by an enemy submarine in the form of a gigantic fish, which takes them to the underwater city Titanica. There, they meet Titan for the first time.

The Stingray crew track the launch site of missiles fired on Marineville to a volcanic island. However, on investigating they become captured by the aliens responsible.

Using an old Spanish galleon, the villainous Idotee is attacking passing ships and plundering them for their cargoes. He soon captures Commander Shore and Phones and holds them prisoner on his ancient sailing vessel.

When the Stingray crew has their holiday abruptly cancelled, they set off to probe the ocean depths. Troy and his friends soon discover a deep undersea shaft, which leads them to a desert-like plateau.

Commander Shore's friend Admiral Denver claims to have seen the Loch Ness Monster. As a result, the Stingray crew travel to Scotland to see if the legendary creature exists.

When Admiral Denver announces his opinion that the WASPs of today would not be able to handle his old-time sailing vessel, Commander Shore takes this as a challenge and assigns Phones and Lieutenant Fisher to the Admiral’s crew.

When a boastful naval Captain arrives in Marineville to demonstrate a new missile, he and Troy immediately experience a clash of personalities. Meanwhile, Surface Agent X20 sabotages the test missile by loading it with real explosives.

While out on escort patrol, Phones hears a mysterious sound through his headset. But when Stingray leaves the escort to investigate, the crew are unable to locate the source. Beginning to doubt his senses, Phones visits a psychiatrist - unaware that the doctor is none other than Surface Agent X20 in disguise.

While the Stingray crew go to the rescue of two crazy treasure hunters, Troy falls down a crevasse, runs out of air and lapses into unconsciousness.

When pop star Duke Dexter pays a visit to Marineville, he causes a commotion amongst his fans. Mistakenly believing him to be a visiting dignitary, Surface Agent X20 kidnaps the singer and takes him to Titan as a hostage.
Created by: Sylvia Anderson, Gerry Anderson
Available on: Associated Television