Incredible Hulk Annual, The (1976 series) #22

Blaming for his wife's death (Betty Ross), Bruce Banner puts a gun on his head. He fails to shoot himself, but the boat he was in sinks and carries him down. Before turning into the Hulk, Banner exhalates the air left in his lungs. The Hulk is saved by Zantor, an underwater scientist working for Attuma. Zantor takes the Hulk into a ship and injects him a water-breather elixir that keeps him alive. This also turns the Hulk's skin to light blue.

The Hulk wakes up very weak and manages to escape. Zantor had taken some of the Hulk's blood and injected it in a friend of Namor the Submariner, turning the man into a gamma spawned monster.

Namor finds the Hulk In the ocean and fights him. But they later join forces to stop the new gamma monster. When Namor's friend is back to normal, he finds himself cured from the plague that's killing all submariners.

Using gamma energy to increase his power, Attuma attacks Atlantis. But the Hulk and Namor stop him by disabling his gamma energy source.

The Hulk turns into Banner who realizes that his blood was used for healing lots of Atlanteans. Namor then takes him to the surface.