WET'N'WILD Sydney Park in Prospect has received mixed reviews from two million visitors since opening last month.
They include Glenmore Park resident Alison Adams and Rochelle Coppini, 19, of Blacktown.
Mrs Adams said she regretted buying gold season passes for herself and three other members of her family.
"We bought them online back in November and they were supposed to be mailed to our home," she said.
"That never happened despite phone calls and emails which received no response.
"We ended up driving to Wet'n'Wild on Christmas Eve to pick them up and, when we asked to buy a fifth pass, we were told they were no longer available.
"Now every time we go we have to fork out $55 for our five-year-old which makes having an unlimited entry pass a bit of a joke.
"They charge $10 for the lockers even though we were given the impression they were free if you bought a gold pass," she said.
"There's nowhere near enough shade or seating and the fact you can't take your own food makes it potentially a very expensive day out for five people.
"It's disappointing given the expectation that was created.
"They have quite a bit to do to improve things. I won't be buying another season pass."
But Rochelle Coppini, who has been to the park twice with four friends, loves it and plans to return next week.
She said they each paid $70 to enter, were at the park from 4pm to closing time at 11pm and had no complaints.
Rochelle wants more restricted Fast-track rides passes to be sold, saying she doesn't mind paying an extra $50 for not having to wait a long time.
"I don't think it's an expensive facility. It's better than the park at Gold Coast and Jamboree Park in Wollongong," she said.
"We don't find the price of food expensive nor suffered any bad effects from the rides as we follow the instructions given by its friendly staff."