Muenster cheese attracts sharks, too, but bloody fish parts are even better and fingers are an especial delicacy. Not sure what the giant squid like though, never seen one eat. ;-).
Please do not feed the fish, even if you are trying to feed them something natural. It lowers their self defense fear of man, and some "tame" fish can and do bite. You can always tell fish that have been fed, they swarm to you and most of them have such lousy eyesight they cannot tell if it is food or your finger. If you get swarmed by fish it usually works to tuck your hands and arms behind your back, they know you are not going to feed them and leave you alone. If there are a lot of people in an area feeding the fish it makes them easy prey for not so honest divers coming after you equipped with a harpoon. The rules are (almost) the same in the water as any natural refuge, take only pictures, don't even leave footprints.
And the best part of NOT feeding the fish is getting to watch their natural behavior. I have snorkeled certain reefs enough to know which rocks are home to which pairs of butterfly fish, which parrot fish is being chased away because he is encroaching, watched an eel being mobbed by all the yellow jack, watched the beautiful turns of large schools, figured out where the tang come out of hiding when you hold still long enough for them to forget your presence, and where the locals go to skewer the "tame, tourist fed" fish.
Carla