Shark meat has an unpleasant taste due to the presence of high concentrations of the waste product urea in the tissue. Sharks store urea to maintain an osmotic balance with seawater so as not to have a water loss problem. Shark reproduction is very different from that of most bony fishes, having a very low output from their internal fertilization and production of large young. Sharks also have very low growth rates, a problem that is related to the problem of overfishing. The most economically important sharks are the sandbar, bull, and lemon which do not mature until about 12 to 18 years of age.
Sharks can see color, as indicated by the presence of cone cells in their retinas.
Similar to cats, they have a light-reflecting layer to enhance their night vision. This is important to divers to realize that swimming and diving in shark infested waters at night is more dangerous. The reason that chumming works so well in attracting sharks is their acute sense of smell. This could be a warning not to dive with even the smallest cut or abrasion. An interesting sense that sharks possess is one called electroreception.