Hoping for a rare opportunity to study the strange amphibian, professor Ferguson (Agar) captures The Fishy One and brings his catch back to a state-of-the-art Florida aquarium.

There, the doc and his assistant Helen (Nelson) try to condition the beast - and to make a few bucks in the bargain by offering it up as a "spectacular" tourist attraction.

But when the Creature takes a liking to Helen, it escapes from its seaside prison...and embarks on a mad rampage through Jacksonville!

Utilizing the timeless blueprint provided by Merian Cooper's King Kong (1933), original Black Lagoon director Arnold injects this followup with some genuinely suspenseful action sequences and effective underwater photography.

Nelson is no Julie Adams, but she and Agar are likable and watchable enough.

Best scene: the Creature unflinchingly slaughters two young do-gooders on the beach.