Siberia's Lake Baikal is the deepest lake in the world, at about 1,640 m, and probably the oldest, at 25 to 30 million years. On its own it holds roughly a fifth of the liquid fresh water found on the surface of the continents, more than all of North America's Great Lakes combined. Its isolation has produced hundreds of endemic species, including a freshwater seal.
On 27 August 1883, the eruption of the Indonesian volcano Krakatoa was heard as far away as Rodrigues Island, nearly 4,800 km away. Its pressure wave was picked up by barometers worldwide and circled the globe several times. The tsunamis that followed killed more than 36,000 people.
The deepest known point in the ocean, Challenger Deep, lies roughly 10,900 m below the Pacific surface. Drop Everest in and its summit would still sit about 2 km underwater. Down there, the pressure is more than 1,000 times what you feel at sea level, roughly a tonne pressing on every square centimetre.