Med schools don’t have many varsity athletes who enter. But if he were to swim for a D1 team, it would certainly be noticed by the admissions committees. They generally don’t make concessions for athletes in terms of GPA and MCAT score though.
Have you considered a post-bacc program? These are designed for students who decide to do pre-med requirements after finishing college. There are some one year programs that lead to a masters degree. This can often be a way to boost GPAs, and make candidates more attractive for med school admissions?