This issue is a reprint of the Sub‑Mariner Vol. 2 #5 (June 1968) storyline, condensed from 20 pages to ~18 pages with about two pages trimmed.

Plot Summary (in more detail):

1. The Setup: Olympic swimmer Todd Arliss suffers a catastrophic injury—left unable to compete at peak performance.


2. Ambitious Experiment: Enter Dr. Dorcas, a scientist determined to restore Todd’s aquatic prowess. He devises a radical experiment: merging genetic traits of Namor (though unknowingly) and sharks.


3. Rise of the Tiger Shark: The transformation yields Tiger Shark, a fearsome hybrid boasting Namor’s attributes plus shark-like predatory instincts.


4. Conflict: Namor confronts Tiger Shark beneath the waves, but the newcomer’s enhanced abilities tip the scales early in the fight—Namor is defeated.


5. Cliffhanger: Seizing his advantage, Tiger Shark captures Lady Dorma, leaving Namor stunned and setting the stage for his desperate rescue.