When I was in Cabo last year, I got to spend sometime in the water with a Blue Shark and it was one of the most incredible experiences of my life. They are so beautiful to see in person
The odds are your best defense in this situation - it’s highly unlikely. If there was a GWS we might even try to jump in with it. But in the worst case, nothing is stopping a GWS. Usually the other smaller sharks will disappear as a sign something bigger is around