It's def not piss.....I've been fortunate to be with girls who can squirt, and I've also managed to make a few girls squirt who didn't know that they could! Once during RO, one wg squirted a little straight into my mouth. Tasted lovely and sweet! "What the fuck was that?" she gasped, bewildered! We then spent the next 30 minutes or so exploring this new talent of hers.....always a good idea to book a twin bedded room if you get a gusher!
However, I've been with a couple of wgs who have been trying "too hard" to squirt and I think they did piss at the same time, which made a bit of a smelly mess on my sheets! I find it's far better if you make it happen, rather than them try to encourage it out with a doxy, etc. They are more relaxed if you are doing it and have less to worry about!
Just my 2p worth...