My experience is with a sand shark. perfectly harmless. He was chasing the small fishes next to the shoreline where we were. There were four of us six feet from shore. Waist deep. Full moon and the Gulf was as smooth as I have ever seen it. Like glass. He was feeding on small fishes near shore and was almost right on us when I pulled my wife away to shore. The women were slightly spooked. When the flash of cell camera flashed, the shark fled quickly away.