It was sudden when the humpback whale popped out of the water at the Hawaiian Island Humpback Whale National Marine Sanctuary near a crew of filmmakers. The large adult, a female, seemed curious.

She began slapping the water with her tail, then swishing it back and forth above the water's surface. The unusual behavior went on for just over an hour. The film crew thought, and hoped, she might be having contractions. Then, as if nothing happened, it ceased. And the whale swam away.

“It just sort of happened out of the blue,” says filmmaker and National Geographic grantee Chris Cilfone. “But that's exactly what we're looking for.”

Cilfone had hoped it would be the moment he would finally film something no