Yeah, yeah, sympathies and all that to the Billy-Bobs what got bit and all…
Sharks are (for the most part) opportunistic feeders. They cull the weak and dying from the seas. Rarely will they expend the energy required to hunt down something healthy and fight with it. Deep water sharks (mako) are more apt to hunt than shallow water sharks (white). There are also regional population differences in eating/hunting habits. The whites off Catalina Island in California hunt differently than those off of Durban, SA.
In general, sharks go for the weak, dying, sick, infirm first, thereby conserving energy. They identify this prey by the vibrations/water disturbances they create. Near a beach, there is lots of vibration drawing sharks, but also confusing them. They may be scared away, or chomp reflexively at something near them - though usually the former.
On the energy idea, sharks feed rather infrequently, whites often going months between meals. Therefore, they tend to go after prey with lots of stored energy (read: fat) this is why seals are so popular on the menu. Surfers tend to look like weak thrashing seals from below (neat studies done off Catalina with surfboards and fins). Sharks will often bite and, if too chewy/low-fat will move on.
I’ve been diving many times with many sharks. I’ve NEVER felt that I was in any specific danger (though always felt quite edgy). I’m too big of a meal, not fatty enough and would fight to the point that a shark would decide I’m not worth the energy expendature. Of course, that would be AFTER the test bite. (hence edgy)
One memorable experience was off the coast when our dive boat was making its way to a wreck 10 mi. off shore. I won’t say where, in that it is a popular beach destination and many of my MD doper friends might get a bit spooked. We were just about 1/4 mile off the coastline when we saw a pod of porposes heading our way. While it’s illegal to approach sea live and harass it, it’s fine if you sit still and let them come to you. We slipped overboard and saited until they swam past us, often circling and checking us out.
Of course, what follows food is that which eats the food. SHARKS. Shortly after most of the porpii (?) left, we found ourselves in the water with 2 BFSharks. We pulled knives and slowly made our way 50 ft or so to the boat as the sharks swam off. Sucked my tank dry at 15 feet!
I’ve also been diving in a big tank with, among other creatures, 5 bull sharks (known attacks on man), but this was at Epcot, so they were Disney sharks. More cute and cuddly than anything else.