Known by many other names (urolagnia, urophilia, undinism, golden showers), watersports is the sexual excitement when thinking about or seeing urine. The fetish is more commonly associated with being covered in urine or covering someone else in it. Some take it even further by getting more arousal when they swallow it or see another swallow it. Often taking place in a bathroom or wet-room, this fetish can create a lot of mess to clean up, sometimes with the receiver doing their duty to make the place spotless again. A lot of the time it is associated with domination, and so the dominant in the relationship will urinate on the submissive, with the submissive accepting it to demonstrate their worth as a slave or as a sub.
Watersports is not something that can be done immediately. It is a fetish that does require preparation to ensure the bladder is nice and full, ready for the treat you'll get later on. If you are the giver, you will need to make sure you drink plenty of fluids beforehand so that, when the time comes, you can perform the way you hope to. If you are the receiver, then make sure you give your partner plenty of notice and set time aside for it. There is nothing more frustrating then not having enough time to prepare and having to try and force it - let it happen more naturally and it will be even more enjoyable for both of you.
During your session the time will come when you or your partner, depending on who is delivering the surprise, will be ready. Take yourselves off to the agreed spot and get ready for the warm golden juice to fall.
Once it is done, why not suggest your partner rubs it in on you, or themselves for you? If you are in a dominant relationship, order them to. You can then carry on as you planned or even jump in the shower together for some soapy fun to wash away the urine.