There was once an undersea post office in the Bahamas.
241
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.
17
Sharks, like other fish, have their reproductive organs in their chests.
248
There are approximately three million shipwrecks on the ocean floor, worth billions in value and treasure.
22
Two dogs were among the Titanic survivors.
262
The Caspian Sea is also classed as the world's largest lake.
52
The North Atlantic gets 2.5 centimetres (1in) wider every year.
119