Reef manta ray

The reef manta (Mobula alfredi) is the world's second-largest ray: its wingspan reaches 3–4 metres, yet it feeds exclusively on plankton. You cannot mistake it for anything else – a diamond-shaped body, black back, white belly, and two cephalic fins ("horns") on either side of its head that it can roll into funnels. When feeding it unfurls these fins, opens its cavernous mouth and strains tiny crustaceans and fish eggs from the water in slow loops and occasional backward somersaults. It has no sting; it cannot bite or hurt you.

Mantas have the largest brain-to-body ratio of any fish, and it shows: they are curious, quick to learn, and return faithfully to the same "cleaning stations", where wrasses pick parasites off their skin. Every individual carries a unique spot pattern on its belly – like a fingerprint – and researchers track them by name from photographs. A female gives birth to a single pup, already nearly one and a half metres wide, only every one to two years, so populations grow very slowly and the species is threatened worldwide.

Around Hurghada the manta is a rare but recurring guest: it appears most often in spring and early summer, when plankton-rich water drifts along the outer reefs – Umm Gamar, Carless Reef and the walls of the Giftun Islands. With luck, one may glide beneath you even while snorkeling. The rule is simple: stay calm, never chase and never touch – the protective mucus on its skin is delicate, and a relaxed diver is exactly the company a manta chooses to linger with.