do a sport in HS cuz you love it; or love the team. I think lots of people have gone through your situations~
e.g.: S18 swam 3 yrs (varsity) in high school; and club swam. he was exhausted during swim season. Swimmer families know all about this! He stopped immediately after his junior year & the state swim meet.
He (and 2 others) ended up coaching a summer swim team through the city rec program. It was the best experience for him: coaching & teaching 90 kids, and communicating and emailing with some hyper-vigilant parents! He has worked at the indoor pool his senior year, just got his pool operators license, taught lessons, and has saved a few kids while on the lifeguard chair. He has also had time to train for cross country/track his senior, which he has enjoyed, although he will not be the top kid.
your son has obviously been trained and knows about swimming; perhaps he can use those skills as a job or volunteer opportunity if he wants.
have a relative who’s a recruiter/HR at fortune 500 Co. She’s told us over the years that she’s interviewed new college grads who list swimming as an activity. As a recruiter she had NO IDEA the amount of time and commitment swimming takes until she saw what our high school kid went through. I wonder if college admissions officers are like that?