As to the question about condoms and chlorine. Chlorine is not condoms greatest enemy, friction is. Chlorine can eventually breakdown a condom but since the condom is going to spend most of its active life inside another body chlorine is not its first concern.
Because sex underwater usually reduces natural lubrication, it is important to apply a silicone lubricant before getting into the water. To use a condom under water the man needs to put the condom on before his penis gets wet or else the condom might slip off during sex.
Of course, the water in the pool or hot tub could be forced into the vagina or rectum causing temporary dryness, irritation and possible infection. It seems that water bound sex is fraught with its own obstacles so perhaps poolside sex might be a safer option but probably not as adventurous. Follow your gut but please use the condom and the silicone lubricant if you’re going to walk (or swim) on the wild side.