Hi Angie, I am pleased you are doing the hydro with a PT. do make your PT aware of your concerns from before regarding slipping.
I did mine with hubby, but was extremely careful. I also got a pair of very light water type shoes with a non slip bottom. I found these gave me such confidence about not slipping. I do a lot of scuba diving and snorkeling and had got the shoes for walking across rocks.. I got them from the dive shop however my pool also sold them.. Great boost to my confidence. I also used my stick getting to the pools edge, then hubby's strength to get it.
Of course once in, there is this wonderful sense of weightlessness, but because of that I was cautious not to overdo it, because as you know it is easy to do more in the water than on the land.
There is a very good book, I purchased on Kindle which focuses on pool exercises, by Robert Klapper MD and Linda Huey.. Can't quite remember the title, but if you search Amaxon ebooks you should find it... It gave me so many hints and tips.
I will be keen to hear how you go - good luck and enjoy!