Now that Waterpia's rates have climbed beyond what I am willing to pay, I am happy to find that Aqua World has an extensive discount this month. I think that the 50% discount will put an adult ticket at around 12,000-15,000won, but I may be wrong.
The complex isn't as extensive as Waterpia's but it does have a good variety of pools.
To get there, take the same bus as for Waterpia; number 3 or 3-1. You need to ask the driver as (and I have never figured out why they don't just add a few more number) only some of the #3 buses go there.