Why wouldn't you be able to go to the water park while pregnant? Sure, there may be one or two things you'd want to skip (or maybe you can do everything, I'm not sure) but early in pregnancy there is essentially no risk to the baby unless you were in a major accident. Once you get to 10+ weeks I would be a little more selective of the activities you do, but you can still ride rollercoasters, swim, run, exercise without any restrictions, etc (this is unless you have medical necessity not to). I think you should still go.