As a guidian to numerous kids in my society, peer pressure is beyond a pressure it's a lifestyle battle for children. Few hours ago, while on a walk, I met four kids heading to swim in a natural pond, which was on same direction to my location, when they got there, one refused to swim, the other three enjoyed their moment while he watched but after a few minutes the child who sat on the shores left and went home.
Get this point, the other 3 didn't brag about being better swimmers, but the other child wasn't feeling cool about not jumping into the water like his friends did, and knows that sooner they'll begin to discuss about that and chose to leave or go home.
Peer pressure is like something that occurs mostly on the kids and this can also be an anxiety because you wouldn't no which of them that's affecting the kids, in regular cases some of the peer pressure are originated from a kid getting bullied by other kids from the same class and they would start reducing there performance and association, sometimes being least intelligent in the class usually affect them because they always get mocked by others who are more intelligent than them. However what you said would have definitely happened because if he was to sticked around when those other 3 children will come out of the water they would definitely say something he might not truly like.