The lifeguard was thankfully "okay" following the abuse, Travers said.
In the early hours of Wednesday morning, about 50 people broke into the park while hundreds partied on Maraetai beach, Stuff reports.
Two security guards were working overnight, but could only watch helplessly as the park was trespassed by the group, Travers said.
He said he understood many of them were drunk and he couldn't afford the risk of someone drowning by acting foolishly on the park.
"I've been up half the night helping security guards watch back the CCTV cameras and try to identify people," Travers said.
However, this wasn't the first time the water park had been targeted.
The closing came after weeks of abuse, vandalism and health and safety concerns.
On Christmas Day, the Maraetai park was targeted when staff – who were 200m from the shore – were threatened by people with knives. The blow-up course was badly damaged, but later repaired.
A police spokeswoman said police received a notification of a trespass issue involving a group of youths at this facility in the early evening of December 25.
" It appears the issue was resolved without police attendance," she said.
In the early hours of January 2, a second incident occurred when the park in Red Beach had its onshore compound raided by offenders.
The blow-up park ended up beached and equipment – including a rescue boat motor and safety gear – was reported stolen.
