I have seen nurse sharks, white tipped reef sharks, grey reef sharks, scalloped hammerheads, and one tiger shark off Maui who was a ways off and eating something (not a diver) when we saw it. I have never been on a shark feeding dive, and never fed anything in the ocean (except the occasional upchucking). Most sharks I have seen have been my size or less,thought the hammerheads, some of the nurse sharks, and the tiger were bigger than me. To minimize the chance of being bitten by a shark (the word attack is not descriptive in all cases) I suggest following these guidelines:
1. Don't feed sharks or hang with those who do
2. Don't spearfish
3. Don't "corner" a shark. My wife and I penetrated the hull of the Cartheginian off Maui, and there was a white tip reef shark inside. All it wanted to do was get out, and we made room for it
to do so.
4. Don't dive unprotected in areas that you know are big shark feeding grounds.
5. Don't dive in shark territory if the viz is under 25 feet (great hunting conditions for sharks)
6. If you have the privilege of seeing a shark in its natural habitat and behavior, and it is a privilege, keep your arms and hands close to your body, move lowly and smoothly, if at all,
and enjoy the experience.
Seeing a shark is wonderful. They are not likely interested in you. Respect them, watch them, be alert but calm, and enjoy the encounter!
As to Barracuda, they like shiny things, but encounters involving a bite are very rare. Avoid necklaces or chains that shine and dangle, and if you are really paranoid, lose your rings and earrings too.
DivemasterDennis