Dillin and Cuidera give Killer Shark an extra long story in Blackhawk 183 (April 1963).
Killer Shark and his crew are back, and raiding ships using an underwater platform as a base. The Blackhawksn manage to get into the platform just as it gets pulled down to the bottom of the sea. It turns out that Killer Shark stole it from a race of bottom dwelling mermen.
The mermen at first see the Blackhawks as being just as guilty as Killer Shark. They had built the platform to battle a big scary fish monster that had been eating them. When they see the Blackhawks risk their lives to help them fight the fish, they decide that they are not as bad as Killer Shark.
Even the mermen think it is fitting that, in the end, it is one of Killer Shark's weapons, used by Blackhawk that gets rid of the fish monster. The mermen agree to let the Blackhawks take Killer Shark back to the surface to imprison.
Killer Shark returns the following year.
The back-up story introduces a new pet for the Blackhawks, a monkey named Bravo. Because yes, someone thought that what the Blackhawks really needed was a pet monkey.
In the story, it's supposedly an animal trainer friend of theirs who sent them Bravo. The Blackhawks aren't sure what to do with the monkey, but the animal eagerly goes into action with them.
Grabbing himself a costume, Bravo helps the Blackhawks defeat Copter Man, but the chimp is really a plant sent by criminals to aid them in a rain robbery.
At the critical moment, Bravo has to choose between the criminals who trained him, and the Blackhawks, who have given him one of their costumes. Bravo chooses to aid Blackhawk and turns against his former master.
Bravo returns a couple of issues down the road.