Containing 97 percent of all water on the planet, these vast habitats are home to some of Earth's most diverse plant and animal populations and have yet to be fully explored.
Take a dip to discover some of the incredible wildlife that make their home in the ocean, from sea turtles and bearded seals to poisonous jellyfish and starfish.
OK, so the Earth's climate is heating up. Hasn't this happened countless times in the past? Is this time really any different? See what today's top climate scientists are saying.
After thousands of years of living in balance as a wild food source for humans, so many giant bluefin tuna now have been hauled out of the Mediterranean that the population is in danger of collapse.