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Blue Planet is back – here's how to visit the incredible locations

Tossing £5,000 worth of electrical equipment over the side of a Zodiac inflatable boat might seem foolish, but the sophisticated piece of gadgetry I’m lowering into the icy Southern Ocean could reward me with far greater intelligence on the state of Antarcticathan any expedition cruise ship lecture or illustrated field guide.

Deployed off Cuverville Island, where moulting gentoo penguin chicks are getting ready for their maiden dip, the CastAway device reveals that water salinity is lower than average – a worrying trend seen in glacial regions at both poles, according to the naturalist Bob Gilmore.

Locked for millions of years in ice sheets smothering the White Continent, fresh water is flooding and diluting our oceans – and I’m seeing it in real time with my own eyes.

Trundling at an idle speed, we trawl a net behind us, collecting samples of phytoplankton, a microscopic marine plant heavily affected by changes in salt levels. The foundation of an aquatic food chain, these translucent organisms are the lungs of the ocean, an invisible force producing 80 per cent of the oxygen in our atmosphere.

“Every other breath you take, think of these guys,” says Gilmore, as floating ice debris gasps and crackles.

Data collected from our excursion will be sent to the Scripps Institution of Oceanography at the University of California as part of a long-term Fjord Phyto study, in which tourists get to play the part of scientists, contributing to important research and – most importantly – appreciating why it really matters.

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