I like water parks, don't get me wrong, and Rulantica does look like a pretty great one, but to be honest, I am at heart a theme park enthusiast, and for that reason, I think I'd like to make the most out of savouring Europa Park itself on my first visit, personally; I get the impression that there's no shortage of things to do in Europa Park for 3 days, whether it be reriding some of my favourite coasters and other attractions, riding new attractions, or something else entirely! Or all of the above! (On my later days, this is; everything will of course be new to me on my first day!)