You were a mermaid. Of course no one knew that, besides your pod and yourself obviously. Not even your best friend Chan (Or Chris) knew about it. You immediately change (shift, transform, etc.) into your tail when water touches your skin.

You were at the beach lounging and tanning when all of a sudden the got blocked by shade. You pushed up your sunglasses to see Chan standing over you. "How come you never get in the water?"