No arrests have been made in the shooting, but a 17-year-old was charged with misdemeanor assault and interfering in an investigation.
Before the gunfire, dozens of children jumped on an officer who was making an arrest, police said.
Several hundred children were ushered to the parking lot to board buses operated by Fort Lauderdale-based Xtreme Trips, which organizes outings for high school and college students, authorities said. Fights then broke out in the parking lot.
Officers found a loaded .22-caliber handgun in the bathroom of one of the buses, but it's unclear whether it was the weapon used in the brawl, Jones said.
Michael Roosevelt, 18, was shot in the leg, and Marlin Laguerre, 16, was injured in the mouth, possibly from a thrown rock, Jones said.
Some members of a large group "had become unruly" while visiting the park, said Wet 'n Wild spokesman Mike Black.
"Our security team worked closely with the Orlando Police Department to remove the unruly individuals as a precaution," Black said in a statement.
Wet 'n Wild is a unit of Universal Parks and Resorts. A message system for Xtreme Trips was full.