Tony Wu / Twinspot snapper (Lutjanus bohar) shoal rushing up to spawn, releasing a cloud of milky white sperm and eggs in the water column. Caroline Islands, Palau, November.

Alex Mustard / Boulder star coral (Montastraea annularis) spawning at night with released bundles of eggs and sperm floating away in the water column, East End, Grand Cayman, Cayman Islands, British West Indies, Car...

Jeff Rotman / Whitetip reef sharks (Triaenodon obesus) pack silhouetted following scent trail in water column, Cocos Island, Costa Rica, Pacific Ocean

Georgette Douwma / Lyrtetail anthias (Pseudanthias squamipinnis) in water column with Peach anthias (Pseudanthias dispar) in background. Indonesia, October

Alex Hyde / Fingal's Cave, showing basalt columns, Isle of Staffa, Inner Hebrides, Scotland, UK, June 2010

Jeff Rotman / Whitetip Reef sharks (Triaenodon obesus) following scent trail in water column, Cocos Island, Costa Rica, Pacific Ocean.

Jeff Rotman / Whitetip Reef Sharks (Triaenodon obesus) following scent trail in water column, Cocos Island, Costa Rica, Pacific Ocean.

Flip Nicklin / Octopus (Octopus sp) baby swimming through water column

Georgette Douwma / Kaleidoscopic image of Basket star (Astroboa nuda) commonly found at night with its rays fully extended into areas of current. It removes plankton from the water column by filter feeding. During the d...

Georgette Douwma / Kaleidoscopic image of Basket star (Astroboa nuda) commonly found at night with its rays fully extended into areas of current. It removes plankton from the water column by filter feeding. During the d...

Alex Mustard / Pair of Shortfin lionfish (Dendrochirus brachypterus) swimming up into the water column and spawning a raft of eggs at night. The male is the larger fish on the right. Bitung, North Sulawesi, Indonesi...

Guy Edwardes / Aldeyjarfoss waterfall, Sprengisandur, Iceland. July 2012