Manta rays are flat, wing-shaped fish related to sharks and stingrays. They have a wingspan that can reach 5–7 metres — wider than a family car is long. Two horn-like fins near their mouth scoop food towards them, which is why they are sometimes called 'devilfish' in old sailors' stories, though they are entirely harmless.
When plankton collects in big, thick patches at Hanifaru Bay during the monsoon season (roughly May to November), the mantas go into a feeding frenzy. They begin swimming in circles, then in tight spirals, stacking on top of each other in a chain of loop-the-loops to trap the plankton. Researchers call this 'cyclone feeding' because it looks like a slow, graceful whirlpool.
At peak times, over 200 manta rays can be in Hanifaru Bay at once. Because they are so large and there are so many of them, you can sometimes lie quietly at the surface and have a manta ray glide just centimetres beneath you, its white belly visible, on its way around the loop.
Hanifaru Bay was declared a marine protected area in 2009. Visitor numbers are limited and snorkellers must follow careful rules to avoid disturbing the rays. The protection has helped manta ray numbers in the area stay healthy, and scientists use photo-ID of each ray's belly patterns to track individuals across the years.