Sounds like the encounter that occurred near Catalina Island. An HB family was moored by the Island and the mother was on a kayak. A GWS tipped the kayak up several feet, and she fell on top of the shark, kicking away from it. She was rescued shortly after by a nearby boat.
I'm curious to see what members of this site and kayak fishing community carry along for protection against such encounters. Statistics are great, but won't tell you if you are in that low-mean sample that does get attacked.