i have been told we are going were hammerheads & bullsharks are,i think i have watched jaws to many times
OK, if you see hammerheads then you will be lucky - don't be worried about them! They will likely be quite far away and often below you. To see them you generally swim out from the reef and stare out and down into the blue very carefully. They are easily spooked and especially don't like noises and bubbles. They are very, very, very unlikely to attack you, even if you got close enough for that to happen. Hammerheads are very beautiful sharks, and move in a very particular way that is really quite graceful.
I am not sure that you are going to see Bull Sharks. The other sharks you might see are threshers - again, if you are very lucky. Threshers are easily spooked too, but are stunning looking, with a very long tail that they use to stun fish with, and huge eyes, like puppy dogs'. Grey Reefs are very common, and they tend to pay less attention to divers. Thet tolerate divers closer to them than some of the other species, but will tend to dash off fast once you get too close. White tip reef sharks are the little sharks that are seen everywhere. They only get to a few feet long and are very slim and lightweight. They eat little reef fish, not divers
The one that you will hear of more aggressive behaviour from are the Oceanic White Tips, or OWTs. They are opportunistic feeders. They live in the very top layer of the coean and trawl around for things to eat. This means that they come into contact with humans quite often, and will test items to see if they are edible, hence they display a certain boldness. Some boats have fed them, the crew thinking perhaps that getting the OWT's in close will lead to happy guests and better tips. This is where there is trouble. Don't let your boat do this if you see it (although it is unlikely they will). Don't snorkel with OWT's. If you are diving and see one, then that's fine. Just stick with the group. There was one attack about 5 years ago on a French snorkeller (no think about the number of divers and snorkellers in the Red Sea each year). The story that went around was that the boat had been feeding, and that she had been very eager to get close and had swum out towards the shark. She got bitten, and it was blood loss that killed here, rather than "being eaten".
Honestly, I actively seek out sharks when I dive. I love them. Just relax and enjoy seeing them, if you do. They are beautiful and pose far, far less risk to you than the act of diving itself does. Once you see one you will probably be hooked on them too.
Best of luck for your trip.