Coral substrate forming an underwater cave, Ras Mohammed National Park, Sharm El Sheikh, Red Sea, Egypt, North Africa, Africa

A myriad of hard and soft corals compete for space on the substrate of the snorkel site known as the Milky Way, Palau, Micronesia, Pacific

A myriad of hard and soft corals compete for space on the substrate of the snorkel site known as the Milky Way, Palau, Micronesia, Pacific

A myriad of hard and soft corals compete for space on the substrate of Darwin's Wall, Palau, Micronesia, Pacific

A myriad of hard and soft corals compete for space on the substrate of the snorkel site known as the Milky Way, Palau, Micronesia, Pacific

Green sea turtle (Chelonia mydas), feeding on the sand near Caye Caulker, inside the Mesoamerican Barrier Reef, Belize

Coral bommies in sandy substrate, Rongelap, Marshall Islands, Micronesia, Pacific

Small Tube Worm (Pomatocerous triqueter), group of tiny colourful individuals on rocky substrate, St Abbs, Scotland, UK North Sea

Stoplight parrotfish nibbles algae from the substrate of a reef in the Florida Keys.