Paul Grogan was played by Bradford Dillman in the movie Piranha.
He is unemployed. He drinks a lot because of the divorce with his wife. He has a daughter called Suzie Grogan and lives near a river. He once worked in a factory.
He helps Maggie trace two missing teenagers by being her guide, which leads them to an abandoned government test site he knew about and therefore plays a role in releasing the piranhas by giving her free hand in emptying the pond at the test site and by stopping Hoak from acting accordingly to stop her.
When he realises, what they have done, he does everything to stop the piranhas, even more so, when he realises that they are like salmon, who live in fresh and salt water. He, like her, then do everything to stop the Piranhas from reaching the ocean. On the way he also helps in saving children, including his daughter.
Later he manages to reach the ocean in time and stop the Piranhas with Maggie's help, while all the time also having to fight the military on the way who want to maintain the Piranhas in secret in the public eye while also ignoring the dangers about them, recklessly endangering the people on the way, too. He does it by unleashing pure poison from a factory he once worked at at the end of the river, but suffers a lot of wounds by approaching Piranhas while doing it. He is then treated by Maggie in the presence of his daughter.
It is implied he will have to face consequences regarding his role in the release of the piranhas.