I’d say that approach works every time, right up until the time it doesn’t. Sharks are nothing if not unpredictable.
Depends on the type of shark we’re talking about. Nurse sharks are as docile as they come, and we used to swim with them as kids. Hammerheads are a little unpredictable, but they’re not the brightest bulbs. I’ve never seen an unmotivated act of aggression from a hammerhead. Again, if you look like prey, they might nip to see.
Bull and tiger sharks, on the other hand, are like pit bulls: unpredictable and dangerous. I’ve been in the water with them, but they always bear watching.
I don’t make it a habit to be in the water with them, but with the right mindset and an appropriate understanding of their behavior, seeing one in the water near you won’t raise such an alarm. Tourists running from the water due to a shark sighting is more apt to trigger an attack than staying in the water and remaining calm. I’m not saying to stay in the water with a shark, but if one is around, calmly make your way to dry land.