Mark Brownlow / Sperm whale {Physeter macrocephalus} diving, tail fluke, Kaikoura, South Island, New Zealand

Mark Brownlow / Rebreather instructor Ian Thomas and cameraman Didier Noirot prepare to dive under the ice, Lake Baikal, world's deepest and oldest (and largest by volume) freshwater lake, Siberia, Russia. BBC Plane...

Mark Brownlow / Aerial view of Bombay Hook NWR, Delaware Bay, Delaware, USA. Salt marsh and refuge for migratory flocks of Greater snow geese. November 2005, BBC Planet Earth

Mark Brownlow / Low aerial view of Iguazu falls, world's largest waterfalls that straddle Brazil and Argentina, Iguacu Falls NP, South America. BBC Planet Earth series. November 2005

Mark Brownlow / Looking down on frozen surface of Lake Baikal, world's deepest and oldest (and largest by volume) freshwater lake, Siberia, Russia. BBC Planet Earth series, April 2005

Mark Brownlow / Aerial view of Bombay Hook NWR, Delaware Bay, Delaware, USA. Salt marsh and refuge for migratory flocks of Greater snow geese. November 2005, BBC Planet Earth

Mark Brownlow / Aerial view of Upper Yosemite Falls in Yosemite NP, California, USA. BBC Planet Earth series. May 2006

Mark Brownlow / Aerial view of Snow goose (Chen caerulescens) flock in flight, part of annual migration, Bombay Hook NWR, Delaware Bay, Delaware, USA. November 2005, BBC Planet Earth

Mark Brownlow / Mark Brownlow, producer of Freshwater programme for BBC Planet Earth series, behind ice sheet, on location at Lake Baikal, world's deepest and oldest (and largest by volume) freshwater lake, Siberia,...

Mark Brownlow / Kukenon, flat top tepuis, southern Venezuela, South America. November 2005, BBC Planet Earth

Mark Brownlow / Aerial view of Bombay Hook NWR, Delaware Bay, Delaware, USA. Salt marsh and refuge for migratory flocks of Greater snow geese. November 2005, BBC Planet Earth

Mark Brownlow / Angel Falls, world's tallest waterfall, southern Venezuela, South America November 2005, BBC Planet Earth