The movie opens with a dead cow in the water, piranha eggs pop out of it's pussy...why?! Why am I wasting my time with this junk when I have a whole stack of Kurosawa and Ozu movies over here? I hate myself and my morbid curiosity...anyway, cow pussy. You gotta dead cow, it's gotta dead cow pussy and out of this dead cow pussy pops piranha eggs. The piranhas promptly go to a nearby water park and eat a bunch of people. Some ugly chicks get topless. David Hasselhoff shows up. The End.
The story, what there is of it, concerns a girl (Danielle Panabaker) bickering with her stepfather about him opening up an adult themed water park and her friends who work at the water park, including a nerd who is secretly in love with her. Yawn. The story is junk, the violence is garbage, the jokes are beyond lame, the nudity wasn't even worth me taking screenshots of and the acting is barely one step above a Troma movie.
The only reason I can think of to watch this stinker is Danielle Panabaker is really hot. Other than that skip it with a vengeance and never look back.
Part 1 - Piranha (1978)
Part 2 - Piranha II: The Spawning (1981)
Remake - Piranha (1995)