["My friend bet me $20 in a swimming race across a lake last weekend. I took the deal because I am positive I'm a stronger swimmer!", "$20 bucks?  I'd try to do it too.  How'd it go??", 'I won of course! The guy was no match for my swimming speed!']
Awesome!  He'll know not to challenge you next time!  $20 bucks richer!
My friends and I were relaxing and swimming at a lake last weekend. My friend bet me $20 that I couldn't race him in a swim across the lake. I ended up winning because I knew I was a faster swimmer.