Some cats dont mind water, like yours, apparently. Some cats don't respond to a loud "no!" which I like to use. Honestly, I think simply removing the cat from the counter 300 times, over however many weeks, is about as likely to be effective as negative reinforcement and not controversial. However, that too is far from a sure thing. That leaves you with solutions that make walking on the counter uncomfortable as that article linked above suggests. Since I find doing that out of proportion to the problem, I just deal with it, and put the training-resistant cat down when its bothering me.
I haven't had a training resistant cat in a while . . . but my current 5 month old kitten is *very* resistant, so I feel ya.
Please don't squirt your cats with water! At best, they won't care. At worst they will either fear you are end up avoiding you in general.
Maybe a loud noise? Hiss at them? That is what another cat would do if they did something to provoke another cat.
We got cheap plastic place mats and covered them with double sided tape and covered the counters with them. Neko-chan hated the sticky on her feet. It took a few weeks but seemed to be a gentle way to train her.