Alex Mustard / School of White collar butterflyfish (Chaetodon collare) pack together above a coral reef. North Male Atoll, Maldives. Indian Ocean

Shane Gross / Moorish idol (Zanclus cornutus) juvenile with transparent skin in the open ocean at night off Anilao, Philippines.

Tim Fitzharris / Butterflyfish (Chaetodon sp) and Sergeant Major Damselfish (Abudefduf saxatilis) school, Negros Oriental, Philippines

David Fleetham / Schooling Lemon / Milletseed butterflyfish (Chaetodon miliaris) below kayakers off Maui, Hawaii.

David Fleetham / Schooling Lemon butterflyfish (Chaetodon miliaris) near to surface. Maui, Hawaii.

David Fleetham / Looking upwards to schooling Lemon butterflyfish (Chaetodon miliaris) near to surface. Maui, Hawaii.

David Fleetham / Schooling Raccoon butterflyfish (Chaetodon lunula) framed in a lava formation off the island of Lanai, Hawaii.

David Fleetham / Schooling Raccoon butterflyfish (Chaetodon lunula) framed in a lava formation off the island of Lanai, Hawaii.

Bert Willaert / School of Longfin spadefish (Platax teira), Kimbe Bay, West New Britain, Papua New Guinea

Alex Mustard / Scissortail sergeants (Abudefduf sexfasciatus) swimming over hard corals (Acropora sp.) on shallow reef at sunset, split level view. Gubal Island, Egypt. Red Sea.

Alex Mustard / Colourful reef scene with Coral grouper (Cephalopholis miniata), map puffer (Arothron mappa) and Panda butterflyfish (Chaetodon adiergastos). Tank Reef, Fiabacet Islands, Misool, Raja Ampat, Indonesia...

Tim Fitzharris / Green Sea Turtle (Chelonia mydas) swimming with a school of butterfly fish, Apo Island, Philippines