I’ve laid a lot of tile over the years, floors and showers. The uric acid in pee will dissolve the grout in the shower’s grout lines assuming you have a nice tile shower. Might damage the concrete liner underneath, too or just hang out there in the concrete above the rubber liner, stinking. Epoxy grout would
probably will hold up better, but it is expensive, a hassle to install, and probably not in your shower. I’ve had to replace entire porcelain floors after renters let dogs/cats/kids urinate on the floor. Not only crumbly grout lines but very difficult to get the smell out (hydrogen peroxide works best). If you have a cheap, plastic/fiberglass shower go ahead and spray, though your shower might start stinking from the drain trap.
Shower water does dilute it and if you rinse it down, probably no damage. Adding an answer from AI here: