Margen
The deepest point of the ocean is in the Mariana Trench, in the Pacific, and it's called the Challenger Deep. There the floor falls to nearly 11,000 metres below the surface.
To picture it: if you took Everest, which is 8,849 metres tall, and sank it there standing up, its summit would sit more than two kilometres underwater. It wouldn't even poke out.
At that depth the pressure is crushing, over a thousand times what you feel at the beach; a lungful of air would compress almost to nothing. And even so, there's life down there: microbes and small animals that thrive in total darkness and cold.
We've walked on the Moon, but very few people have gone to the bottom of our own sea. The most extreme place on the planet is right at home, covered by water.