Global stats on shark attacks confirm that swimming, wading, snorkeling, and surfing are dangerous in terms of shark attack. SCUBA is not on the menu so to speak. Last year a recent article sited only one shark attack on a SCUBA diver and he had a game fish he had just killed. In 2002, the figure was 2 divers. One was a shark diver operator who hand feeds the shaks while his customers watch. Well, he, ah, er, well
he hand fed the shark. The other SCUBA diver had his leg bitten as the shark tried to get at the game fish he had killed.
Bottom line, don't act like a seal and thrash around on the surface and you most likely will be fine. On the very rare occasions I have seen a shark (blue shark) it was a beautiful experience and one to be enjoyed, not feared. I dive Southern California and have yet to see a Great White. They inhabit our waters and give birth here. Of all the divers I know, only one has reported a sighting while diving. That was in Malibu last year with 15 to 20 foot visibility and it was a baby Great White he saw at only 10 feet length and at 15 foot range. He is still in one piece and reports wetsuits are rather easy to clean.
Statistically, in the world most shark attacks occur in Florida in one county, so don't wade in the waters of this one county.