Other shark links:
Worldwide Shark Attacks
Great White Attacks
The relative risk of a shark attack is very small (The Relative Risk of Shark Attacks to Humans Compared To ...) but, risks should always be minimized whenever possible in any activity.
The chances of having an interaction with a shark can be reduced if one heeds the following advice:
Always stay in groups since sharks are more likely to attack a solitary individual.
Do not wander too far from shore --- this isolates an individual and additionally places one far away from assistance.
Avoid being in the water during darkness or twilight hours when sharks are most active and have a competitive sensory advantage.
Do not enter the water if bleeding from an open wound or if menstruating --- a shark's olfactory ability is acute.
Wearing shiny jewelry is discouraged because the reflected light resembles the sheen of fish scales.
Avoid waters with known effluents or sewage and those being used by sport or commercial fisherman, especially if there are signs of bait fishes or feeding activity. Diving seabirds are good indicators of such action.
Sightings of porpoises do not indicate the absence of sharks --- both often eat the same food items.
Use extra caution when waters are murky and avoid uneven tanning and bright colored clothing --- sharks see contrast particularly well.
Refrain from excess splashing and do not allow pets in the water because of their erratic movements.
Exercise caution when occupying the area between sandbars or near steep dropoffs --- these are favorite hangouts for sharks.
Do not enter the water if sharks are known to be present and evacuate the water if sharks are seen while there. And, of course, do not harass a shark if you see one!
[Reprinted, from: Burgess, G.H. 1991. Shark attack and the International Shark Attack File, pp. 101-105. In: Gruber, S.H. (ed.). 1990. Discovering Sharks, American Littoral Society, Highlands, New Jersey]