There's just something about worrying about the statistically super unlikely event of being predated upon by the marine killing machine known as a shark. Little mammal fears eh? Out of our terrestrial environment... The potential risk (admittedly small) of an encounter with a predator who is very well adapted to the marine environment... ZOMG!
Other posters have hit the nail on the head as far as what's more likely to kill you. Maybe we should focus on ways to keep those damn terrestrial mammals in their element and out of the water (and I'm not talking lemmings here folks)[and yes, I know that the "lemming mass suicide" thing is b.s., just a bit of humor folks...]