The diver you see here is a bro named Eli Martinez, an editor for Shark Diving magazine (hell yes it's a thing). This awesome picture with a lemon shark was taken in The Bahamas. Here's what he had to say about the encounter:
This particular shark I had encountered before. She is very laid-back so I knew if I held my hand out she would come over. At first she was swimming straight towards me, but I didn't expect her to turn at the last moment. She tapped my palm with her fin like we were high-five-ing.
Super chill. My Shark is a Bro, coming to a bookstore near you Shark Week 2012.