Swim, surf or dive with other people, and don't move too far away from assistance. Stay out of the water at dawn, dusk and night when some species of sharks move inshore to feed. Do not enter the water if you have open wounds or are bleeding in any way.
Sharks can detect blood and body fluids in very small concentrations.
These types of waters are are known to be frequented by sharks. Do not wear high-contrast clothing or shiny jewelry. Sharks see contrast very well. Sharks are known to be attracted to such activity. Do not enter the water if sharks are are known to be present, and leave the water quickly and calmly if one is sighted.