It's pretty clear that the Size 0 look isn't the norm. The average dress size in the UK, for example, is a 16 - meaning that the overwhelming majority of women don't fit what we currently consider to be the "ideal" body size. The good news is that "ideal" is absolute bullshit; everyone is different, everyone's body is different, everyone's health is nobody's business but their own and everyone finds different things attractive.
There are plenty of people who enjoy being on the larger side, and even more whose type in women runs to the curvy. Whether this forms part of a fetish or is simply a matter of aesthetic preference depends on the individual - but whichever side of the line you fall on, it's important not to run the risk of fetishising a person in a way they haven't consented to.
The term 'watersports' covers all sexual pursuits involving urine, and it's pretty common amongst kinksters. If you're new to this fetish and you'd like to try it out, the best way for beginners is to hop in the bath or shower with your partner before you play: it keeps things contained and makes it much easier to clean up afterwards!
In contrast to scat, watersports don't usually come with heavy hygiene warnings; piss is a lot cleaner than people give it credit for. Make sure your golden shower is a fresh one, though, when pee starts to go stale it can also start causing you harm.
So there are two main issues with sex in the water. One is that it tends to wash away a lot of the essential lubrication, meaning that things can get a little paradoxically dry down there - and the other is that water's natural buoyancy means it can be a bit more difficult than you might imagine getting everything in place. The trick is to bring some water-based lube in with you, anchor yourself on the side of the pool and keep experimenting till you find something that works for you and your partner! This is an experience well worth having, though it might take a little while to get it right.