Alex Mustard / Midnight snapper (Macolor macularis) shelters in a cavern on a coral reef with white soft corals (Scleronephthya sp.) and solderfish. Vavuu Atoll, Maldives. Indian Ocean

Alex Mustard / Schools of Pacific creolefish (Cephalopholis colonus) and Panamic sergeant major (Abudefduf troschelii) swimming through sun beams inside an underwater cavern. Los Islotes, La Paz, Baja California Sur...

Alex Mustard / Shoal of Bar jacks (Caranx ruber) hunting school of Silversides fish (Atherinidae) in coral cavern. East End, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Inaki Relanzon / Lesser Horseshoe Bat (Rinolophus hipposideros) hibernating in Forat de l'Or cave in Terradets Canyon, Pyrenees, Lleida, Catalonia, Spain, December

Alex Mustard / Diver swimming through dense school of Silversides (Atherinidae) inside a coral cavern, Grand Cayman, Cayman Islands, British West Indies, Caribbean Sea. Model released

Jack Dykinga / Roots of Fig trees (Ficus sp) growing in the collapsed Cenote Oxpeejool (sink hole), near Tekax, Yucatan, Mexico. Afternoon light illuminates the elongated cavern on the right. October 2009

Jack Dykinga / Stalagmites and stalactites in underground cavern with tourquise waters of Cenote Papakal (sink hole), near Merida, Yucatan, Mexico October 2009

Jack Dykinga / Cenote Samula (sink hole) with elongated roots of a Fig tree (Ficus sp) from ground level descending to the subterranian tourquoise coloured water below. Rays of sulight pass through the hole to illum...

Claus Meyer / Visitors explore an expansive cavern with stalactites, Vale Do Peruacu, Minas Gerais, south Cerrado savannah, Brazil

Alex Mustard / Tarpon (Megalops atlanticus) hunts silversides (Atherinidae) inside a coral cavern. George Town, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Alex Mustard / Bar jack (Caranx ruber) hunting a school of silversides (Atherinidae) in a coral cavern. George Town, Grand Cayman, Cayman Islands, British West Indies. Caribbean Sea.

Franco Banfi / Scuba diver at the cavern limit sign, Tajma Ha cenote, Quintana Roo, Yucatan Peninsula, Mexico. May 2015.