Jacob "Jake" Forester was played by Steven R. McQueen in Piranha 3D.
He goes with a porn director and two porn actresses in order to help them film a porn movie against his mother's wishes who wants him to look after his younger siblings while she is working. He does this in exchange for money by guiding him and the rest of his crew to the best places in the lake for the movie he intends to make.
For this purpose he bribes his younger siblings into not telling his mother so that he can go while they promise him not to leave the house. His girlfriend follows him. Later, however, he has to rescue his younger siblings when they leave the house against what they agreed. During these events, he realizes the porn director is dangerous.
When the piranhas come, he has to watch how they decimate the crew and harm the ship, but he can save his girlfriend and, with the help of his mother, kill the piranhas, which turn out to be baby piranhas.
It is implied he will go with his family to Spring Break and go away from the town after finding out about the adult piranhas.