Anxiety over body when swimming

So I'm a 20 year old man and my little brother is 11 years old. If you look at the first pic below, you'll see he's stronger than the average kid. He's on the left and I'm on the right. The other day he challenged me to a wrestling match where he got me in the move seen on the last pic below, I tapped out (submitted) but he said he wouldn't let go until I said that "I was his b*tch" which I just said because I couldn't breathe. He still didn't let go and I passed out. So yeah, he pretty much established that he's stronger.

I have to go swimming with my family today and I'm really insecure about my body. I don't want people/my parents thinking my little brother looks stronger than me. Am I exaggerating in my head how bad my body looks? Do you think I look stronger than my brother?