Juergen Freund / Bean shaped polyps of an Anchor coral (Euphyllia ancora), a large polyp stony (LPS) coral. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Detail of a soft coral (Dendronephthya sp). Misool, Raja Ampat, West Papua, Indonesia

Alex Mustard / Boulder star coral (Montastraea annularis) spawning at night, showing the very start of the the release of bundles of eggs and sperm, East End, Grand Cayman, Cayman Islands, British West Indies, Carib...

Alex Mustard / A Symmeterical brain coral (Pseudodiploria strigosa) spawning at night, releasing pink and white bundles of eggs and sperm from the polyps within its grooves, East End, Grand Cayman, Cayman Islands, B...

Alex Mustard / A Symmeterical brain coral (Pseudodiploria strigosa) spawning at night, releasing pink and white bundles of eggs and sperm from the polyps within its grooves, East End, Grand Cayman, Cayman Islands, B...

Alex Mustard / A Symmeterical brain coral (Pseudodiploria strigosa) spawning at night, releasing pink and white bundles of eggs and sperm from the polyps within its grooves, East End, Grand Cayman, Cayman Islands, B...

Alex Mustard / A Symmetrical brain coral (Pseudodiploria strigosa) preparing to spawn at night, showing the bundles of eggs and sperm within the polyps prior to their synchronous release, with a Triplefin (Helcogram...

Alex Mustard / A Symmeterical brain coral (Pseudodiploria strigosa) preparing to spawn at night, with one gamete bundle beginning to be released, East End, Grand Cayman, Cayman Islands, British West Indies, Caribbea...

Alex Mustard / Two photos of a Symmeterical brain coral (Pseudodiploria strigosa) spawning at night, showing views before and during the release of the gamete bundles, East End, Grand Cayman, Cayman Islands, British...

Alex Mustard / A Symmeterical brain coral (Pseudodiploria strigosa) preparing to spawn at night, with one gamete bundle beginning to be released, East End, Grand Cayman, Cayman Islands, British West Indies, Caribbea...

Alex Mustard / Close-up of a Mountainous star coral (Montastraea faveolata) preparing to spawn, East End, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Alex Mustard / Great star coral (Montastraea cavernosa) photographed at night under blue light to excite the fluorescence, Little Cayman, Cayman Islands. Bristish West Indies, Caribbean Sea.

Alex Mustard / Great star coral (Montastrea cavernosa) at night, photographed under blue light to excite the fluorescence, Little Cayman, Cayman Islands, British West Indies, Caribbean Sea.

Alex Mustard / Great star coral (Montastrea cavernosa) at night, with polyps extended and feeding, photographed under blue light to excite the fluorescence, Little Cayman, Cayman Islands, British West Indies, Caribb...

Alex Mustard / Coral fluorescence photographed at night under blue light to excite the fluorescence, this image is probably a colony of knobby star coral (Solenastea hyades), Little Cayman, Cayman Islands. British W...

Alex Mustard / Lamarck's sheet coral (Agaricia lamarcki) close up, East End, Grand Cayman, Cayman Islands, British West Indies, Caribbean Sea.

Juergen Freund / Close-up of Soft coral (Alcyonacea) with open polyps. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Fluorescent Mycedium coral (Mycedium elephantotus) in normal light. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Detail of a soft coral (Dendronephthya sp). Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Detail of a soft coral (Dendronephthya sp). Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Fluorescent Mycedium coral (Mycedium elephantotus) in normal light. Misool, Raja Ampat, West Papua, Indonesia.

Juergen Freund / Sea thimble jellyfish (Linuche unguiculata), Rowley Shoals, Western Australia

Juergen Freund / Surface detail of soft coral {Dendronepthia sp} Indo Pacific

Roberto Rinaldi / Coral (Favia sp) fluorescence at night, captured using an electronic strobe, Red Sea.

Roberto Rinaldi / Coral (Favia sp) fluorescence at night, captured using electronic strobes, Red Sea.

Roberto Rinaldi / Detail of a coral anemone (Corallimorpharia), Kudat, Sabah, Borneo

Roberto Rinaldi / Hard coral (Favia sp) fluorescence at night, captured using an electronic strobe, Red Sea.

Roberto Rinaldi / Close up of hard coral polyps, Philippines.

Roberto Rinaldi / Coral (Favia sp) fluorescence at night, captured using an electronic strobe, Red Sea.