Don't worry Ayla!! It happens to the best of us
Even though I've been offering watersports for years, I still get a shy bladder as well sometimes! And I know you've said you're new to it, and maybe you haven't had / don't want to have a guy pee on you, but trust me it happens the other way round too. Guys often really want to do it to us as well, then in the moment find they can't. It's just one of those things. I think that we all have it so ingrained into us that you only pee on the toilet that randomly pissing anywhere else can be difficult... it's a natural mental block.
What helps me is having a really chilled relaxed atmosphere.... I tell the guy it might not happen straight away and lets just relax (in position in the bath) for a few minutes first. Chatting is fine if he likes that but "crouch over me / piss in my mouth " type talk or trying to play with me makes me lose focus and is too much pressure. Within 2 or 3 minutes of the relaxed time, knowing there's no expectation, I will be able to have a nice wee (and probably be unable to stop-but that's a whole other story
)
I know it goes without saying, but really needing to pee is important too. When I first started doing watersports, the only way I could do it would be to drink so much water that essentially I was just uncontrollably wetting myself once in the desired position. It does work though! Obviously this has to be timed very carefully... don't even THINK about trying this ahead of time or if you are travelling to the booking by car. Xx