no no no...no feeding of sharks for me. I don't know how common swimming with sharks is, but my dive instructor has a video of a shark swimming around them in the Bahamas while he was diving off the live aboard Julienne. My thinking is this. If you're underwater, then you're just another marine lifeform. If you're on the surface, then you're a wounded marine lifeform. Surfers are more likely to be attacked than divers I think (no factual data to back that up, just anectdotal) thus my concern.
I had thought about trying to keep eye contact, if only to know what they're doing. I know they're most sensitive on the snout and punching them (easier said than done I'm sure) might work. And I've even seen on the discovery channel if you swim TOWARDS them then they lose interest in a hurry (gotta love shark week). It's just the actual practice of surfacing and getting on the boat without attracting a circling shark to begin with is my concern.
Another thing. Vertical or horizontal on the surface? Again, horizontal probably looks more like fish, especially with fins on.
NO, you do NOT watch sharks to keep an eye on them..... You watch sharks conspicuously so
THEY know you are keeping an eye on them. Any one of them can shoot in take off most or all of your calf and if you did not have a stick or weapon there would be absolutely nothing you could do about it, even if you watched them really well.
Of course that hardly ever happens, (except to a local guy about 8 months ago).... but the point is that.. sharks are not stupid, they are good predators, these types of predators know where you are looking, they will try to sneak behind you and if they get in that position, they may be more emboldened than otherwise.....
You don't let a curious, stray dog trot right up behind you without turning to face it (if you have a choice)... I've seen COUNTLESS times where (when carrying a dead fish) a small shark will begin following the diver, but the second you spin round and give them the evil eye, they bolt.
When this happens with a much larger shark, their response is often considerably less deferential. We have to realize that we are bluffing, a big shark could easy kill a diver... So I try to take on an attitude of : "I SEE you", "I will NOT let you get behind me", I am NOT trying to evade you, and if you come in that close again..I'm going to poke the crap out of you with the pole spear (I pretty much always carry).
It is hard to make generalizations because the situation can go from calm to bad quickly, if several excited sharks begin to become competitive around you. A diver could find themselves in a situation where the sharks have recently fed on a fish that was caught by a fisherman (or a spearfisherman).
There are many other clues sharks MAY give as they get amped up, but keeping you eye on them is important. That is exactly why a bunch of aggressive sharks can be very bad, you simply can NOT watch a bunch of sharks zipping around you, and if you begin to start frantically trying to spin around to face them, you can begin to look weak, worried and struggling...so that is why you can try to back into you buddy and ascend together, back to back, each try to watch a 180 degree hemisphere of water.
If you are not spearfishing and the sharks are not being fed, 99.99% of the time just watching them and letting them know you see them and are not acting "prey-like" is enough to ensure that you don't really have to worry about the other stuff.