Mike competes with a pair of helmet divers to salvage a German submarine sunk off the coast of South America.

A killer whale is capsizing boats and endangering scuba divers and swimmers along a stretch of coastline.

Mike plays commando in rescuing a scientist who had defected from Soviet kidnappers who are returning him to Moscow aboard a Pacific liner.

Mike dives into the Caribbean to recover the lost nose cone from an ICBM rocket before enemy agents can get it.

A pair of ruthless treasure hunters dupes a young skin diver into helping them loot a sunken ship.

An attractive magazine photographer hires Mike to assist her in getting pictures of a sunken barge off the coast of Mexico.

Hired to test a new electronic fish-finder, Mike encounters a village where every fish in the vicinity has disappeared.

Mike helps the Immigration Department Border Patrol break up an underwater border-running operation.

A beautiful woman hires Mike to give her diving lessons for mysterious reasons.

Before Mike can investigate the disappearance of a pair of skin-diving geologists, one turns up dead on the beach bearing marks resembling the suction valves of a giant octopus.

While investigating the cause of a mine flood that killed thirty men, Mike stumbles upon an air pocket with two survivors.

A grudge between two divers whom Mike is testing for underwater mining skills becomes a secondary issue when one of them contracts nitrogen narcosis.

Mike tries to free the pilot of a downed jet from his watertight cockpit before his air runs out, without causing the man’s death from the water pressure.

Villains go after Yancy’s dog after Yancy’s father dies leaving a note that only the dog knows where the family pre-war fortune is buried.

Yancy tries to find out who’s responsible for recent grave robberies.

Shop owners receive threats of violence if they refuse to sell their property to three strangers.

An army officer with vengeance on his mind tries to stop a presidential pardon from reaching a man who is scheduled to die before a firing squad.

A wealthy but lonely man who has come to New Orleans looking for a wife asks Yancy to help him.

A messenger is sent to New Orleans by a former general in the Civil War, but is killed before he can reveal what happened to a fortune that was taken…

After administrator Colton hangs a member of an outlaw gang, the others decide to take revenge on his visiting sister.

An Irish girl visitng New Orleans decides that Yancy is to be her future husband.

Yancy is relieved to find that a newspaper story about administrator Colton’s death is premature, but fears that Colton will be the victim of trickery in an upcoming duel.

City administrator Colton entrusts Yancy with an army payroll that is to be taken to Natchez on Yancy’s riverboat, the Sultana, but robbers have other plans.

Yancy helps a sea captain who was cheated out of his money in a dive on notorious Gallatin Street.

Yancy wins enough money playing poker to pay for his return home to New Orleans. The losing players decide to rob him of his winnings, but he escapes on a…