Okay, 6 month old Maine Coon Kitten boy, neutered. I was sat on the toilet, kinda minding my own business, little boy comes into the bathroom and jumps into the empty bath. That's not too unusual, however, squatting over the drain hole and having a wee was a new one on me. Apart from getting his paws wet in the expanding yellow puddle - leading to a spray up the bum from the shower-head (which he didn't like - maybe a bit cold for him), and copious amounts of bath cleaner sprayed around I think we got away with it this time.

So... how to kitten-proof a bath??

I don't think its a case of kitten-proofing the bath, rather making him realise there is a proper place for peeing!
When he squats, grab him and put him on his tray. He should learn that that is the place to go.
At least the bath is easily cleaned - next time it might be behind the sofa or on your favourite rug!

You could put a tray in the bath room I suppose - just in case he's copying you.

Close the door.

Funny thing is I think he is copying... he is fully litter trained - there's been no problems there (until now), but he always joins either of us in the bathroom for whatever purpose.

Cats like going to the toilet in a clean place. As the bath/shower gets used regularly it probably feels to the cat like the cleanest place. I'm not suggesting the litter tray is dirty, just that the bath is cleanest.

Have you got more than one litter tray? That might help. One of my cats went through a phase of pooing in my shower, did it for a couple of months on and off, and then stopped one day. The litter tray is rarely used now they go outside, it is in the bathroom though, and I use decent quality litter, so it reduces the smell (for the cats, not me)

That is hilarious.

Try putting a litter tray in the bath

Ha ha, my cats done this. I left about and inch of water in there, never saw him go in it found wet paw prints along the floor the next day, and he's not be back since (except when I had to bath him be ause he was covered in shampoo-that's another thread!)

All joking aside, I'd get a vet check, utis are really common in cats and sometimes the look for new places to pee as the associate their usual areas with the pain, baths are quite common. Hopefully it's not that, but is be checking just incase