Most sharks live in the tropics. Most shark attacks occur on boats. The largest sharks eat microplankton. Dogfish Sharks can rest on the seafloor so long as a strong current moves by their gills. Sharks have a blood salinity closer to freshwater than do salmon.
Sharks expend a great deal of energy parenting.
Both Great Whites and Hammerhead Sharks have attacked humans. Sharks have a lousy sense of smell.