The blacktip reef shark is relatively small reaching a maximum length of only 6'. Blacktip reef sharks usually stay clear of people - unless a diver is carrying speared fish. This species inhabits shallow reefs throughout the tropical Pacific and Hawai'i, and can often be seen with the black tip of its dorsal fin projecting from the water. Sharks are not the only hunters on coral reefs. The white jack, or ulua aukea, is the largest species reaching a length of five feet and weights of over one hundred pounds.
Jacks are voracious predators and are most active just after sunset when they feed on reef fish.
Sharks and jacks are both fishes, but spend a few minutes comparing them and see how different they are from each other. Look at the shape of the fins. Notice, too, how different shark's and jack's tails are. And internally, sharks have lightweight skeletons made of cartilage much like the material in our ears. Jacks have skeletons made of hard mineralized bone similar to our own.