This is when you ask someone to high five you but you put your arm in a wave motion and touch their cheek twice with your index finger or you can give them a slap. Slaps are most common. This is usually used within the UK.
Johnny: Hey Bob! High Five!
Bob: *lifts hand in the air preparing for high fave*
Johnny: *moves hand in wavy motion around Bobs hand and slaps or touches Bobs face and says Scubadive*
Bob: WTF MAN!