I would talk to their supervisor. It seems at our neighborhood pool that all the employees are quite young, college age perhaps,even the supervisors. This does mean that they are learning and may not be very skillful if this is their first year doing this.
It also sounds like the two instructors haven't figured out how to work together. There were 6 kids in my grandson's class (level 1) and the two instructors freqently worked with just 3. That way there were only 2 to keep track of while they worked one on one with 1 of them. They also required the kids to sit on the steps in between each step in the lesson. That provided a structure that kids this age need.
If they have other classes at that level perhaps you could ask for different instructors. I've taken my granddaughter to the free week and once to lessons during the summer for 3 years now. I added my grandson who has difficulty talking and is easily distracted this year. His instructors were so great with him. They tried using a time out which of course didn't work. They took me to their supervisor who suggested that he take private or semi-private lessons and because he has an IEP (Individual Education Plan) they would be free.
What I'm trying to say is that the Grant pool (Portland Parks and Recreation) people have always been helpful and the ones I've seen are well trained. I've been surprised at how calm they remain in the middle of the hub bub. So I think it's possible that your pool staff will work with you to find a way for your son to learn.
High fives must be the norm now. Our pool's instructors do a high five for each one if they try each step in the lesson. My grandkids have done high fives since they were 2 or 3 and eat it right up. Another sign that they use is "thumbs up." I use that sign when I'm not near them but see what they're doing.
My granddaughter is so cute, of course. She gives my a thumbs up or a high five when I've done something for her.