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 beast exists.

Shore takes up Admiral Denver's challenge that the WASP's of today can't take the rigours of an old-time sailing vessel. Phones and Lt. Fisher are assigned to Denver's crew. When a storm hits, Denver is knocked out and loses his memory and Phones and Fisher are cast adrift in a small dinghy. They are rescued by Troy who has been following in Stingray but, when Stingray approaches the sail boat, Denver begins firing his guns wildly at the sub. Troy, however, succeeds in overpowering Denver who later regains his memory in hospital.

Phones is convinced that he is unfit for duty when X20's plan to discredit him nearly succeeds. Disguised as a psychiatrist. X20 further discredits Phones' claim that he really did hear the sounding that drew Stingray away from their escort patrol. It's Lt. Fisher who discovers X20's remote sounding device that clears Phones.

Thinking all the commotion at Marineville signals the visit of a VIP, X20 kidnaps the man and delivers him to Titan. The undersea ruler is surprised to learn that X20 has brought Duke Dexter, a pop singer. Titan is convinced that Dexter is an ally of the underwater people by the way he drives the Terraneans crazy with the weird noises he emits. Dexter is freed by Titan to continue his 'good work'.

The Stingray crew aid Professor Graham in his search for the missing temple of Tajmanon which was submerged when a dam was built in Africa. They encounter incredible dangers until they meet with El Hamra, an old colleague of Graham's who tells them that the temple was moved stone by stone to dry land.

In an effort to brighten the Christmas of the orphaned son of an ex-WASP Aquanaut, Troy asks him to join the Stingray crew in the re-enactment of the battle when a mysterious enemy craft was abandoned. Unknown to anyone, a member of the crew is still aboard when Phones takes command. Held at gun point, Phones is forced to draw Troy into a trap but the Stingray captain manages to rescue his buddy and solve the mystery.

Lt. Fisher takes command of Stingray in his training to become an Aquanaut. The exercise involves target practice on a Terror Fish target but X20 has attached a sticker bomb to one of the targets and one to Stingray's hull. Troy is air-dropped into the sea in an attempt to remove the bomb from Stingray's hull before it explodes.

While the Stingray crew are on shore leave in Casablanca, a merchant sells Phones a map leading to ancient treasure. However, when Troy refuses to search for it, Marina secretly alters Stingray's course.

A film crew arrive at Marineville to make a movie on Stingray. Everyone will play themselves except Troy, who is to be replaced by an actor. What's worse is that the director is in fact Surface Agent X20 who has a plan to kill Troy !!

The Stingray crew is captured when aliens set up a trap at a weather station. During what appears routine questioning, they unsuspectingly give away vital secrets about Marineville. While Stingray is on patrol, the base is attacked from below. The Invaders are unaware that Troy is aware of the invasion and they are taken by surprise when Stingray comes to the rescue.

As part of his plan to destroy Marineville, Surface Agent X20 infiltrates the base by posing as a professor who can teach mute people to speak. Then, unknowingly, Troy and Phones place Marina in his hands.

Atlanta is captured by an undersea race when Stingray investigates the collapse of an oil drilling rig. She discovers that the creatures only attacked the rig out of self-defence, believing that their home was under attack. Unfortunately, a bomb has been planted aboard Stingray that will explode when the ship dives. Atlanta makes a desperate effort to contact Stingray but, fortunately, Marina's pet seal, Oink, discovers the bomb and pushes it off in time

Professor Darren has developed a way to make gold from minerals on the sea bed. Agent X 2 Zero spies on the first test run & reports to Titan. Titan wants to destroy the Prof.'s Bathyscape & Stingray in one go when Stingray calls to collect the gold & deliver supplies to the Professor. Troy manages to save the mining operation & outsmart Titan once again.!