Dr. Robert Hoak was played by Kevin McCarthy in the movie Piranha.
Dr. Hoak was a team member of Operation Razorteeth with the purpose to create piranhas that would be later spread on the river system of the North Vietnamese during the Vietnam war. When the war ended, the piranhas were poisoned and the team was disolved. He, however, stayed with the purpose of continuing the experiment with the piranhas that survived the poisoning with the purpose of making them even stronger and more intelligent creating a species that would also survive in salt water.
One day two teenagers, ignoring the warning of not entering, entered the place with the purpose of making a bath in the pool, where the piranhas were. They were killed by the piranhas with Hoak not being able to do anything about it. He took their things away with the purpose of telling the first one searching for them what happened without telling them about the experiment. One day Maggie and Paul reached the place searching for them. When they found the things they wore, they drained the pool for the purpose of seaching in it. Hoak tried to stop them and was overpowered by them. An attempt to warn the authorities by using their car failed, when he became the victim of an accident
The next day, when Paul and Maggie went down the river, because Hoak had harmed their car, Hoak, having overcome the trauma of the events, told them everything after introducing himself to prevent them to put their hands into the water.
He sacrificed himself to save a boy from being eaten by the piranhas and died. Maggie and Paul later threw him into the river in order to save themselves from being killed by the Piranhas, when they attacked their raft.