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One of Martyn's diving companions, Robbie Schmittner, in a huge flooded cave in Mexico.
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Divers carry remote underwater flash guns to illuminate this image, taken in what is probably the world's biggest underwater tunnel, Weebubbie Cave beneath the remote Nullarbor Plain of western Australia.
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% E$ U/ @ W! j4 X) ]1 e5.39.217.77:8898Divers often use guide-lines to keep them on track in the murky depths. Getting lost can be fatal.
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; R9 X) n+ |, O, e9 iDeep and dark doesn't always mean cold: Jenny Pinder swims through the underwater passages of the Grotta Giusti Cave in Tuscany, Italy. where geothermal activity heats the water to an amazing 35 degrees centigrade
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In another of Martyn's photos Helen Rider swims through the narrow confines of Taina Cave near Santo Domingo in the Dominican Republic. |