Don Winslow of the Navy

Cmdr. Don Winslow

Mercedes Colby

Spencer Merlin

Lt. Red Pennington

Misty Gaye

Mike Splendor

John Blake

Paul Barsac

Henchman Corley

Henchman Spike

Seaman Chapman

Henchman Prindle

The Scorpion

Gang Radioman Barker

Lt. Cdr. Grady

Admiral Warburton [Ch. 1]

The CINCUS [Ch. 1]

Capt. Holding [Ch. 1]

Enemy Sub Capt. Tranker [Ch. 1]

Capt. Fairfield, of the "Batavia" [Chs. 1-2]

Tangita Jim [Chs. 2, 10]

Capt. Sanders, of the "Tarleton" [Chs. 3-4]

Saboteur Kramer [Chs. 3-4]

Lead Henchman at Mill [Ch. 5]