Answer:
Something you can do is find a different activity that has to do with water/the pool that has the same difficulty as tricks on the diving board
Step-by-step explanation:
As someone that almost drowned, people have taken extreme caution when I'm around water, so much so that I don't really have fun. Find something your friend can do that won't make them feel uncomfortable or set them apart from the others like underwater tricks or underwater basketball (actually really fun but you have to buy a special ball) while the rest of you dive. Maybe don't dive at all if they feel left out. Don't force them to do it for the "good" of everyone else.