I went to WaterWorld in early October - for the end of the holiday season there were only about 50…read morepeople there.
The price is EUR24 with an option to buy tickets for another day at EUR12. There are also deals which tie in locker hire, mini golf and use of the sun loungers. There was also a tie-in with another water park, but it was shut from late September so we were unable to check that out.
I quite enjoyed the park itself, there were a good range of rides for all the family and the aforementioned 16-hole mini golf course which isn't brilliant but well worth a go. If nothing else, WaterWorld will keep you fit from walking up and down the steep hill. Quite sensibly the bulk of the kids pools and slides are at the bottom of the hill.
The food and drinks were fairly cheap compared to most theme/water parks.
There's a free shuttle bus to Lloret de Mar, and other free buses to Tossa de Mar, Fenals and other local resorts.
I'd highly recommend going there,