I have two swimmers and both of them have had children with ASD in their groups. The kids all seem to get along fine as long as everyone follows directions and learns swimming etiquette. One of the swimmers with ASD did not follow proper lane sharing etiquette at all, so the kids got annoyed at him for that. The coach knew and enforced what he could. (For example, you order the lane by speed in a particular stroke/distance. This swimmer would lead in backstroke and not give up the lead, even when the set switched to breast or fly and wouldn't let kids pass him.) The coach had to reorder that lane himself every time, which is kind of crazy when you get to high school.

Swimming is a fabulous sport. Hope your kid ends up loving it!