Sharks run (uh.. "swim") rampant in Oregon; more there than any other coastal state I've lived in; Hawaii included.
You basically learn to just vacate the water when you see one, and if it turns out to be a dolphin or a seal... you head back out.
Seals, dolphins and otters have shared waves with me (they're playful, social animals... otters being the least playful of the three)... I've been able to see sharks before both from a pier and from shore, but.. yeah.. when that's the case, we don't go out.
A friend of my Mother-in-Law was killed by one a few years ago.
http://articles.sfgate.com/2003-08-2...ck-avila-beach