"As the white shark population rebounds and seal populations rebound, this predator-prey relationship is going to re-emerge anywhere these two species overlap,” Greg Skomal, a leading Atlantic great white shark expert, tells Nat Geo. Below, a crush of gray seals along Monomoy Island, off the Cape Cod town of Chatham, Massachusetts.

These days, Brian has been on assignment diving off the coast of New Hampshire and Maine, focusing on lobsters and colorful anemones. He says he won’t linger near the surface (where sharks feed on seals), but acknowledges he’s “very concerned.” “The notion of diving in cold waters, with limited visibility, having my head buried in my viewfinder, focusing on a lobster on the sea floor and looking up to