Can I assume he doesn't do this when just you are in the pool? I take it he has been trained to stay out of the pool and even though he is heeding your training and request, he might just be expressing himself the same as if the pool edge is similar to a fence.....
Maybe acclimating him to the notion that all is well by staying at the edge of the pool when you are in it and allowing the dog to have contact with you...and slowly work some distance into it as the dog keeps it's crap together. If your pooch has a reasonable down/stay...I would utilize that and expand on it.
I used to watch my neighbor's dogs do the same when people were in their pool and it seemed to work itself out over a short period of time. I'll have to remember and ask them how they dealt with it.
It's a shame you can't have your boy in the pool with you.