Alex Mustard / Orange painted frogfish (Antennarius pictus) resting between the venemous spines of a Fire urchin (Asthenosoma varium), Batangas marine protected area, Luzon, Philippines. Verde Island Passages, Pacif...

Alex Mustard / Pygmy lemon gobies (Lubricogobius exiguus) pair, guarding their home in a glass bottle, Batangas marine protected area, Luzon, Philippines, Verde Island Passages, Pacific Ocean.

Alex Mustard / Coleman shrimps (Periclimenes colemani) pair, female on right, camouflaged in their Fire urchin (Asthenosoma varium) home, Batangas marine protected area, Luzon, Philippines. Verde Island Passages, Pa...

Alex Mustard / Saddleback anemonefish (Amphiprion polymnus) and a Spotted porcelain crab (Neopetrolisthes maculatus) living together in an anemone. Bitung, North Sulawesi, Indonesia, Lembeh Strait, Molucca Sea.

Alex Mustard / A diver swimming through the Silfra fissure, a crack in the Earth's crust between the North American and Eurasian continental plates, which is filled with glacial melt water. In this photo the Am...

Alex Mustard / Pygmy seahorse (Hippocampus bargibanti) among a Sea fan (Muricella sp.) on a coral reef, Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Alex Mustard / Marine iguana (Amblyrhynchus cristatus) feeding on green algae on seabed, with more iguanas on the surface behind, Cape Douglas, Fernandina Island, Galapagos Islands, Pacific Ocean.

Alex Mustard / Mexican hogfish (Bodianus diplotaenia) male, with Pacific creolefish (Paranthias colonus) behind, swimming over reef, Darwin Island, Galapagos Island, Pacific Ocean.

Alex Mustard / Three Stingrays (Dasyatis americana) swimming over sand in shallow water, The Sandbar, Grand Cayman, Cayman Islands, Caribbean Sea.

Alex Mustard / Two divers exploring the bow of the USS Kittiwake wreck (a US Military submarine rescue vessel deliberately sunk as a diving attraction in 2011), Seven Mile Beach, Grand Cayman, Cayman Islands, Caribb...

David Perpinan / Flathead grey mullet (Mugil cephalus) and Salema (Sarpa salpa) school swimming past the camera in the mouth of the Besos river. The fish enter and leave frame. Barcelona, Spain. October.

David Perpinan / Catalan chubs (Squalius laietanus) swimming around, showing interest in the camera. The fish enter and leave frame. Besos river, Barcelona, Spain. October.