I have surfed when sharks were present.
Down in los angeles when i was growing up, a buddy and I were surfing. We had each just ridden a wave, and were paddling back out, then we realized that everybody had dissapeared.
Then a lifeguard truck pulls up to the edge and yells at us through the loudspeaker to get out of the water.
We hadn't heard him the first time, because we were pushing through the waves to get out (surf was kinda big that morning). Which is why everybody else had gone to shore. Several mako sharks had been spotted in the immediate area.
That is my most interesting shark story, I do have a couple others though.