Jack was played by Keenan Wynn in the film Piranha.
He was a friend of Paul Grogan. He lived near the river and also near Grogan's cabin. He brought liquor to Grogan from time to time whenever he wanted it. He liked fishing with his feet being underwater while also having brandy with him. He had a dog, who was always with him.
When Grogan went with Maggie to the abandoned military installation, he was about to do that again, as he already told to Grogan before this event. When the piranhas at that installation were later released into the river because of Maggie's and Grogan's actions, he became their first victim the next day.
They attacked him while he was fishing again the way he liked at the river, like he did the day before, and devoured the lower part of his legs. Because of that, he later bled to death, when he left his place at the river after that in a vain attempt to save his own life. His dog mourned because of his death.
Jack was later found by Grogan and Maggie because of the dog's crying and they buried him according to his wish not to be buried in town in the case of his own death. This event led them to realise in full, that Dr. Robert Hoak, who was with them, was telling the truth regarding the threat of the piranhas and, haunted by what they did, they became fiercely determined to limit the damage they had done through their actions.