What is that?

One thing about me, is I am a big guy but I will switch on the panic button in a heart beat. In most instances it served me well. In some instances I am totally cool and calm. However we were snorkeling and the view was amazing. Literally like being in an aquarium, so nice so tranquil, so beautiful on the reef. All of a sudden I look behind me about 20 feet below. I see this gray figure. I asked myself, "what is that". Then it moved. I instantly knew what it was. A 7 foot shark. Cool and calm Anthony did not exist anymore. I will be honest, I screamed shark and scrambled to get back into the boat. There was another person in the water with me. I assumed he did not hear me the first two times I said Shark. I zoomed past him apparently pushing him out of the way. I think I know how Jesus and Chris Angel did it now (exaggerating a little, but not much). I walked on water more like ran, and jumped in the boat flippers on and all. I banged my knee up pretty good but I still have my legs. I then got my friend out of the water as the rest of my party laughed at me and then I was told that it was the wrong thing for me to do. For the record, if I see a bear, I will not play dead either. He has to work for his food. I am running. Catch me if you can. I have already put that scenario to the test. I am still here, and that is another story all together.