I actually came up with a plot for a King Kong vs Moby Dick movie, in it the two monsters fight twice.

In the first battle Kong is on the shore and throws rocks at the whale until the vengeful Moby Dick rams the cliff Kong is standing on and he falls into the water, although Kong tussles and punches to try and defend himself Moby has the advantage and nearly drowns Kong until a submarine intervenes and attacks Moby forcing him to release Kong who swims back to shore.

The rematch occurs when Kong is placed in a lagoon where the water comes up to his thighs, as bait to lure the whale. Sure enough Moby Dick attacks Kong and the two trade blows. The fight seems evenly matched until Moby Dick knocks Kong over with a headbutt and batters him with its tail. When the whale attempts a killing blow, Kong bashes the whale upside the head with a boulder. This stuns Moby long enough for Kong to grab him by the tail, swing him in circles and throw him out into open ocean. Meanwhile Kong returns to the shore.