Off the tip of Mexico's Baja California Peninsula, divers were surprised by a rare sight: a cormorant bird diving into the water and plucking a remora off the side of a whale shark. Cormorants always feed by diving for fish, but apparently, no one had ever filmed the birds fishing this way. The footage, filmed about six years ago, resurfaced recently online. Experts can't say if it’s a novel behaviour or just something that hadn’t been recorded. Remoras, or suckerfish, attach themselves to large hosts, living off scraps. In small numbers, remoras are harmless to whale sharks—maybe even beneficial, removing pests. But lots of remoras could be a problem—slowing the shark down, costing energy gained by filter feeding. If a cormorant lightens the whale shark's load, it might be providing a service.