Chlorine alterntive

My boyfriend is allergic to chlorine, so bad that he has never taken his own children swimming. He legit blows up like a puffer fish and cannot breathe.

Today my little boy came up and asked me why daddy couldn’t come swimming with him and Uncle Justin (my boyfriends brother) I didn’t have an answer other than “it’ll make daddy poorly”

Mason hates that he cant take our son swimming and we are looking for an alternative to chlorine if there is one as my parents are moving into a new build house with a swimming pool and want to try and make the effort to try something different for both my boyfriend and my sons sake.

Any suggestions would be greatly appreciated.