Underwater photography - readers' pictures

Dave Johnson: This is one of the enigmatic dugongs that roam the Red Sea around Marsa Alam in south-east Egypt. They are solitary creatures and are usually seen feeding among the sea grass in the various coral fringed bays. This one was over deep water at Marsa Mubbarak. Photograph: Dave Johnson/GuardianWitness

E Wallace: My fourth visit to the same coral and a pygmy sea horse finally looked at me! Photograph: ewallace/GuardianWitness

Dan Massie: Frogfish use their lure to attract their prey. I waited quite some time for this one to launch its lure and open its mouth wide open. Photograph: danmassie/GuardianWitness

David Portman: Grey reef shark Photograph: David Portman/GuardianWitness

James Hardcastle: Green turtles near Lady Elliot Island on the Great Barrier Reef. These two males charged each other and were pecking away, really bad-tempered. I happened to be in the middle, and they completely ignored me. Lady Elliot Island has very accessible lagoon and coral heads and is inhabited by turtles year round. Manta ray, sharks and large grouper are also highlights. In spring, the sound of whales cruising past the island provides a unique underwater chorus. Photograph: jameshardcastle2012/GuardianWitness

Khaled Mahgoub: I took this shot of a scary stonefish when I was working in Nuweiba in the Sinai, Egypt, as a dive instructor. I found it on a dive site called the Pipe Line. Photograph: Khaled Mahgoub/GuardianWitness

ID306923: Anemone fish Photograph: ID306923/GuardianWitness

Richard Littlewood: A smiling moray eel, taken with an Olympus camera up nice and close with a flash. Photograph: Richard Littlewood/GuardianWitness

naushad1slanddivers: A snorkeller with a whale shark in the Maldives. Photograph: naushad1slanddivers/GuardianWitness

David Jones: The aptly named crocodile fish lies motionless on this piece of wreckage. Photograph: David Jones/GuardianWitness

E Wallace: A mantis shrimp taken in shallow water at the end of the dive. Photograph: ewallace/GuardianWitness

David Jones: In Akumal lagoon in Mexico turtles feed on the sea grass. Every now and then they come up for air, and if you are lucky you can get a half-and-half shot. Photograph: David Jones/GuardianWitness