My HOA wants dogs and people to be able to swim in the same pool that is earmarked only for people. What are the health risks?
Brucellosis, Campylobacter, Cryptospoidiosis, Ehrlichosis, Hydatid disease (echinococcus), Leptospirosis, Listeriosis, Ringworm, Toxocariasis and Yersiniosis, to name a few, can be spread from dog to humans who share swimming water. (Longer list in second source).
Maybe you could make a bet with your HOA and if he/she can spell them, then everyone gets to swim with these cooties.
BUT, your question what what is the risk? That is very hard to quantify. In fact, public health law has nixed this practice so effectively, that it is nearly impossible to say what the risk is (just as we do not have good risk estimates for conditions like untreated syphilis).
Your HOA could counter: "lets see the list of diseases that HUMANS can pass to humans in swimming pools", and that list, mark my words, is indeed scary.