The Harbor Patrol asks the Nelsons to retrieve two drums containing toxic waste from the ocean.
A man (Donnelly Rhodes) hires Mike to teach his paralyzed wife scuba diving---only to fire him when the therapy begins to show results.
When Mike (Ron Ely) is hired to study the proposed site of an underwater park, his life is threatened by men who are illegally mining the mineral-rich area.
The Nelsons investigate a marina construction company that is setting off explosions that are disturbing an underwater volcano.
A Federal agent (William Taylor) hires Mike to gather evidence on a crime boss who's planning a drug scam.
The Nelsons help a pearl farmer (Lisa Lau) catch the thieves who've been stealing from her each year at harvest time.
Jenny and Mike agree to help a man (John Allen Nelson) who claims he's looking for the wreck in which his brother died.
Two brothers (Terence Kelly, Denis Blouin) charter the Sea Hunt for a diving expedition, hoping to discover where a previous owner of the boat hid stolen treasure.
While scuba diving, the Nelsons discover the wreckage of a plane---which involves them in a plot to steal computer software.
Jenny falls for a man (Michael Sabatino), who's attempting to salvage gold coins from a shipwreck so he can fund a marine-mammal rescue center.
When Jennifer fails to return from working on a research project in the Caribbean, Mike risks his own life to search for her.
A magic trick turns deadly when Mike makes the acquaintance of a temperamental illusionist who's trying to perfect his underwater escape act.
A best-selling adventure writer who challenges Mike to a scuba race.
Mike becomes suspicious of a woman's motives for taking diving lessons when he learns that she's afraid of deep water.
Mike is hired by a professor at the Marine Institute to search for fossils and runs up against two young thugs’ intent on finding the fossils before him. Bernardo, a young Mexican boy helps Mike locate a safe entrance to an underwater fossil cave.
Mike comes to the aid of his former diving instructor, a cantankerous old man (Barney O'Sullivan) on the trail of sunken treasure.
Mike and Jennifer rescue two injured divers, who later claim to have seen a beautiful woman underwater and heard bells ringing.
During a diving expedition off a remote island, Jennifer and Mike are unwittingly drawn into the path of assassins who are plotting to kill a Latin American official.
Mike learns that the two men who chartered the Sea Hunt to go scuba diving are really seeking safety from hit men.
Mike is happy to see his old friend Jason Stallworth again after many years but becomes suspicious when Mike catches him talking with a dangerous criminal.
Drug smugglers (Colby Chester, Dale Wilson) take Jennifer hostage and force Mike to retrieve a cocaine package from the ocean floor.
Through a powerful underwater video camera, Mike watches two men hide something near a coral reef and his further investigations lead him to a spy ring.