In water, the shark dominates completely. On land, the gorilla wins by default. Realistic encounters favor the shark.
This matchup only works in shallow water where both can operate. In the ocean, the gorilla drowns. On land, the shark suffocates. In shallow coastal water, the shark's 5,000-pound body and devastating bite give it a massive advantage over the 400-pound gorilla.
The gorilla is a poor swimmer with no aquatic combat experience. The shark is an apex oceanic predator with 300 serrated teeth and ambush capability from below.
The gorilla is more intelligent and has grasping hands. In very shallow water where it can stand, it might avoid the shark's attacks. But it has no offensive tools that threaten a 5,000-pound shark.
12:1 weight advantage in the shark's home environment. Devastating bite. Ambush from below. The gorilla is hopelessly outmatched in any aquatic setting.
The shark wins in any water scenario. The gorilla wins on land. Since the fight only makes sense in water, the shark takes it.
Silverback Gorilla also fights
Great White Shark also fights