The film begins as two slackers, Bones Conway (Pauly Shore) and Jack Kaufman (Andy Dick) work at "Crazy Boys" discount electronics store in Glendale, California. While they goof off on the job, both have aspirations of opening their own electronics store in the future. Both are fired though, after destroying a rack of televisions sets.
Looking to score some quick start-up money for their store, and believing that the commitment will be minimal (they are easily lured by the recruiting slogan "One weekend a month, two weeks a year"), the two join the United States Army Reserves. Bones chooses water purification for their field since his brother was an experienced pool man and the field appeared to be devoid of combat. After surviving basic training, they attend water purification training. The two meet up with Christine Jones (Lori Petty) a female recruit longing for infantry, and Fred Ostroff (David Alan Grier), a skittish dental student. The foursome adopts the nickname of "waterboys". The group then returns to Glendale.
What Bones and Jack do not realize, however, was that Libya has been planning an invasion of Chad, and they are consequently called up for service overseas. They first try to get a military discharge by pretending to be homosexuals, but they fail.
Upon arriving in Chad, the four do not get along well with the full-time soldiers, particularly Special Forces Sergeant Stern (Esai Morales). On a routine mission to resupply a forward base, their convoy is ambushed by a Libyan commando squad. The misfit reserves are thought to have been killed in action (KIA) and are left to fend for themselves. After a few days lost in the desert, they are captured by the Libyan forces and spend a night in a Libyan POW camp. There the reservists meet up with Sergeant Stern who has been shot and captured in an ambush. He briefs them on his failed mission to rendezvous with two HALOed Fast Attack vehicles and destroy mobile Scud launchers carrying missiles armed with chemical warheads aimed at American bases in the region.
During an airstrike, the four reservists and Stern escape and find the Fast Attack vehicles. They make contact with the American headquarters and are ordered to finish the Special Forces' mission. After locating the missiles, they have a difficult time holding off a battalion of Libyans while painting the missiles with a laser for an incoming airstrike. The airstrike goes off-target, forcing the reservists to destroy the missiles themselves. Bones grabs an AT4 anti-tank rocket launcher and destroys the Scud launcher base in one hit, but not before accidentally firing one rocket backwards, forcing the group to use the last RPG they have.
The "waterboys" return home as heroes. At the end of the film, they open up their electronics shop next to an Army recruiting station.
Pauly Shore - Private First Class Bones Conway
Andy Dick - Private Jack Kaufman
David Alan Grier - Private Fred Ostroff
Esai Morales - Sergeant Stern
Lori Petty - Private Christine Jones
Lynn Whitfield - Drill Sergeant Ladd
Art LaFleur - First Sergeant Brandon T. Williams
Fabiana Udenio - Gabriella
Glenn Morshower - Recruiting Sergeant Richard Day
Beau Billingslea - Sergeant Daniels
Peter Spellos - Mr. Quinn
Brendan Fraser (uncredited) - Link