We see the Creature from the Black Lagoon abduct Julia Adams and take her back to his cave. But once in the cave, we see a female Creature from the Black Lagoon walk into the cave, and pointing to Julia Adams, she angrily brains the Creature with a rolling pin.
Then we cut to an underwater divorce court, and the female Creature from the Black Lagoon divorces the Creature and is also awarded the cave and custody of their little Creatures from the Black Lagoon.
And then we cut to the Creature jumping onboard the Rita and rampaging around, attacking everyone in revenge for luring him into abducting Julia Adams and losing his family.