The ASWJ, a national Sunni Muslim group, had booked out the entire park for its "strictly brothers only" event, which was attended by an estimated 800 men and boys.

On the day, ACM's Illawarra Mercury has been told female staff went home distressed at the treatment they received, after being told "you shouldn't be here" and being subjected to intimidation and degrading treatment.

This included being called "bitch" and "slut" by a group of the park visitors, the Illawarra Mercury has been told.

Park management said it had a report of "derogatory and degrading treatment" of one staff member and would investigate further if any more complaints came to light.

A source with knowledge of the situation said he knew more than one staff member was subjected to this.

"Whether there were complaints made or not I don't know, but there were multiple girls affected on the day," he said.

"Young blokes were affected too, because they were sticking up for the girls."

Staff had been directed to employee counselling services if they needed them.

The ASWJ said it was investigating, and was committed to addressing the matter.

"While incidents involving a small minority can occur in large gatherings, we want to assure you that we have strict agreements with park officials to promptly address any misconduct and enforce park rules," a spokesman said.

The Illawarra Mercury received complaints about discrimination against female staff who had been directed to wear long sleeves and tights under their shorts - after an initial request that there be no women working there at all on the day.

Park management said all staff, male and female, wore tights and long sleeves for this booking, the fourth by this group.

"As the day drew to a close it [was] reported to us of an instance whereby a team member was spoken to in a derogatory and demeaning manner," a Jamberoo Action Park spokesman said.

"In all cases, we take the safety and wellbeing of our team extremely seriously, and are concerned that such behaviour has been displayed.

"We have contacted team members today to make sure we are fully aware of instances and concerns that arose yesterday, and have offered the support of Jamberoo Action Park and our Employee Assistance Program providers in the meantime.

"As a result of any forthcoming information and investigation, we will work together with the group organiser to ensure future access is prohibited."

Jamberoo staff members had to cover up for the day, wearing long-sleeve shirts and long tights under their shorts, with temperatures above 29 degrees amid 75 per cent humidity.

The Mercury understands ASWJ had asked for no female staff to be working on the day, but park management declined and instead directed staff to cover up in order to cater for religious sensitives.

The ASWJ invitation to members advised that "this is a Mens and Boys only event" and that "Awrah needs to be covered so bring appropriate swimming attire". (Awrah refers to intimate parts of the body, over which different Muslim groups have varying definitions).

Police said no complaints had been made to them.

The source with knowledge of the situation said the request for no women "should have been a red flag" from the start.

But a Jamberoo Action Park spokesman said it adopted the dress code to be "inclusive". It was the group's fourth annual booking.

"Jamberoo Action Park is an inclusive operation and we do our best to accommodate for group individual groups needs were appropriate," a park spokesman said.

"It has been the case while this booking has been in place, that all attractions team members, male and female, have worn long sleeve attire."

The Mercury sought comment from the ASWJ in Wollongong and head office in Melbourne.

"ASWJ acknowledges your concerns and takes them seriously," a spokesman said.

"We are currently investigating the complaints made against our patrons at Jamberoo Recreation Park.

"Over the past four years, we have successfully collaborated with park management to ensure a positive experience for all attendees.

"While incidents involving a small minority can occur in large gatherings, we want to assure you that we have strict agreements with park officials to promptly address any misconduct and enforce park rules."

The ASWJ has had its share of controversies, particularly in relation to radical preacher Sheikh Feiz Muhammad, whose video lectures include one titled "Don't Let the Filthy Western Culture Influence You".

In 2005 he made international headlines after giving a speech in Bankstown where he said women who were raped had themselves to blame for exposing their skin.

"A victim of rape every minute somewhere in the world. Why? No one to blame but herself. She displayed her beauty to the entire world ..." the Sun-Herald reported at the time.

"Strapless, backless, sleeveless, nothing but satanic skirts, slit skirts, translucent blouses, miniskirts, tight jeans: all this to tease man and appeal to his carnal nature."

He compared a woman dressed in such a way to a sheep, asking "Would you put this sheep that you adore in the middle of hungry wolves? No . . . It would be devoured. It's the same situation here. You're putting this precious girl in front of lustful, satanic eyes of hungry wolves. What is the consequence? Catastrophic devastation, sexual harassment, perversion, promiscuity."

Sheikh Feiz Muhammad spoke at the ASWJ annual conference in late January.

ASWJ said the dress code for staff was part of its productive "collaboration" with Jamberoo.

"Additionally, in our initial discussions with Jamberoo management, efforts were made to accommodate our guidelines for dress, reflecting the collaborative nature of our partnership," the AWSJ spokesman said.

"We are committed to addressing this matter thoroughly and maintaining a respectful and enjoyable environment."

There were also a number of visitors kicked out of the park for misbehaving on the rides.

"On this day, there were concerns raised about some guests inability to follow safety directions and procedures of the rides and attractions," the Jamberoo spokesman said.

"This resulted in a handful of guests being asked to leave the facility, which is standard practice if this is identified on any operational day. This was addressed with the group organisers which were extremely receptive and apologetic, and made efforts to communicate with their members about expectations for the remainder of the day."

The Mercury has been in contact with multiple people who were aware of the incidents on the day but were reluctant to speak publicly.

One source said there were several parents of staff members at the water park on Tuesday seeking explanation.

The park was closed; it reopens on Thursday.