Each year since 1991, shark specialists Jeff Carrier of Albion College (Michigan) and Harold "Wes" Pratt of NOAA's National Marine Fisheries Service have returned to the remote islands of the Florida Keys to study the mating habits of nurse sharks. The sharks return each year to an ancient shallow-water breeding ground, which affords a unique opportunity to study their behavior in the wild. This year, National Geographic is along for the ride, and contributing its Crittercam technology to the scientific expedition.

Despite their prominent place in the food chain, surprisingly little is known about the reproduction of sharks. Researchers have taken advantage of a shark "nursery" in a Bahamas lagoon to catch, examine and release a large number of baby lemon sharks. The studies have revealed some of the breeding secrets of sharks.

Shark nets are being removed along South Africa's most popular holiday coastline to reduce the high toll they're taking on other forms of marine life, including harmless shark species. The country's leading anti-shark protection authority believes it can be done without unduly endangering bathers.

For some beachgoers, fear of sharks is as much a part of the summer scene as suntan lotion. The reality is you're far more likely to be killed by lightning. The sharks, however, are besieged by the planet's most efficient predator—humans.