Claudio Contreras / American crocodile (Crocodylus acutus) rear view of animal swimming away over seagrass bed, Banco Chinchorro Biosphere Reserve, Caribbean region, Mexico

Claudio Contreras / American crocodile (Crocodylus acutus) split level with animal resting at surface in shallow water over seagrass bed, Banco Chinchorro Biosphere Reserve, Caribbean region, Mexico

Juergen Freund / Dugong (Dugong dugon) in the seagrass bed shadowed by a trevally. Dimakya Island, Palawan, Philippines

Alex Mustard / A Leafy Seadragon (Phycodurus eques) swims over a seagrass bed. Wool Bay Jetty, Edithburgh, Yorke Peninsular, South Australia, November.

Juergen Freund / Dugong (Dugong dugon) feeding in the seagrass bed with trevally fish inspecting the disturbed sand. Dimakya Island, Palawan, Philippines

Onne van der Wal / Young man snorkeling over seagrass bed, holding a starfish, The Grenadines, Caribbean. February 2010, Model released.

Juergen Freund / Saltwater crocodile (Crocodylus porosus) swimming at water surface, split-level, New Guinea, Indo-pacific

Shane Gross / A Banded sea krait (Laticauda colubrina) searches a seagrass bed for food, off North Sulawesi, Indonesia.

Shane Gross / Sea anemone in the middle of a vast seagrass bed attracts a hub of sealife. North Sulawesi, Indonesia.

Shane Gross / A Banded sea krait (Laticauda colubrina) searches a seagrass bed for food, off North Sulawesi, Indonesia.

SCOTLAND: The Big Picture / Seagrass (Zostera marina) bed, Scotland, UK, May.

SCOTLAND: The Big Picture / Seagrass (Aplysia punctata) bed with a sea hare, Scotland, UK, May.