He said there were no locals involved, in fact, a member of the Black Power gang offered to assist staff to deal with the incident.
"The team did a really good job. It was only when it moved out into the car park that the police had to be brought in."
He said the fracas would be reviewed by the council on Monday to reinforce that public safety was being protected.
"It needs to be safe. It's a family destination. If people want to go there and cause trouble they will not be welcome."
A member of the public who was there took to Facebook to express their disgust at the behaviour.
"We all at Splash Planet and a scrap starts ... in the kids areas ... you people are suck."
Another witness said there was lots of noise and shouting while the fight continued in the car park.
Splash Planet is owned and managed by the Hastings District Council and was re-opened for the summer on November 14.
In last July, it was voted the sixth best water park in the South Pacific in the Tripadvisor travellers' choice awards.