As David Attenborough reflects in his new documentary Ocean, "After living for nearly 100 years on this planet, I now understand the most important place on Earth is not on land, but at sea". We wholeheartedly agree - and urge governments convening at the 3rd United Nations Ocean Conference (UNOC3) in France next month to remember that life below water goes deep. Everything below 200 metres - the deep sea - works silently to keep Earth habitable.