According to the IPCC, more than 90% of the extra energy building up in the climate system since the 1970s has been stored in the oceans. The atmosphere, where we feel warming day to day, has taken only about 1%. That is possible because water holds enormous amounts of heat: the top few metres of the ocean store as much as the entire atmosphere.
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.