More than a dozen men have stood on the surface of the moon, but only three have been to Challenger Deep in the Marianas Trench, the deepest known spot in the ocean.
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The Caspian Sea is also classed as the world's largest lake.
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There was once an undersea post office in the Bahamas.
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Tidal forces between the Earth and Moon are slowing the Earth down and pushing the Moon further away.
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If Antarctica's ice sheets melted, the worlds oceans would rise by 60 to 65 metres (200 - 210ft) - everywhere
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The North Atlantic gets 2.5 centimetres (1in) wider every year.
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Scientists have confirmed that Enceladus, one of Saturn’s moons, has a watery ocean.
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