lick

Today I was in the pool with my younger sister. She bobbed underwater then came right back up. I asked her what she was doing and she giggled and said "I licked you!". For some reason, I didn't feel it. She kept doing it because she thought it was super funny. This isn't the first time this has happened at swim practice last winter, I didn't feel one of my friends licking me until I saw her doing it. Why do people lick me and why don't I feel it???