Is that because the higher river volume causes the water at the ocean near the river to go murky - thus sharks will attack more often thinking the human is something else?
Another question - I like Sunset, Pipeline and Waimea Bay. Is that a high shark attack area? ( I should add, I surf those beaches on the easier days) 
Another question - do you know if Laird Hamilton has ever had an encounter? Those guys spend a crazy amount of time out there.