"Devil's Triangle" is the story featured in issue #40 of Action Man
Action Man is being driven by a Hercules plane to the Bermuda Triangle, where a misterious cloud appears. The Hercules instruments go crazy and it heads straight to the cloud. Action Man tells Mac, the pilot, to eject, while he parachutes himself and his Deep Sea Vehicle.
Action Man drives the Deep Sea Vehicle through a fierce whirlpool, and finds the Hercules on some kind of undersea complex. It belongs to Dr X, and his henchmen capture Action Man. Action Man is reunited with Mac and other prisoners, and Mac explains how Dr X's machine works: X beams a magnetic pulse to confuse navigational systems, turbines create a whirlpool that sucks in anything within range, and pressurised gas is pumped out to disguise the location, creating the cloud. After the explanation, Action Man knocks X's guard out.
Dr X is about to trap the Sultan of Brunei's plane when he finds the gas pump and the whirlpool have been reversed, driving the complex to the surface. Action Man congratulates Mac on his technical work, but mac asks where is Dr X. Dr X is escaping on a boat, but he finds a misterious light and disappears. Action Man fills a log saying that Dr X's boat was discovered drifting empty, so Dr X may have fallen victim to the real Bermuda Triangle...