Submerged Underwater

Under the blue, where the breath begs to be let go, you swim in the stillness, sucking in slowly growing thoughts of air, while straining to keep your composure under the growing pressure. The deep doesn't have much to say, only a constant stream of bubbling nothing that begins to drive you mad as the absence of birds and breeze seem further and further away. Three quarters of the planet Earth are covered by water. A majority of the planet's solid surface is abyssal plain, at depths between 4,000 and 5,500 metres (13,000 and 18,000 ft) below the surface of the oceans. The solid surface location on the planet closest to the center of the orb is the Challenger Deep, located in the Mariana Trench at a depth of 10,924 m (35,838 ft) under the sea. The density of water causes pressure that increases dramatically with depth. The atmospheric pressure at the surface is 14.7 pounds per square inch or around 100 kPa. A comparable water pressure occurs at a depth of only 10 m (33 ft). Thus, at about 10 m below the surface, the water exerts twice the pressure (2 atmospheres or 200 kPa) on the body as air at surface level. For solid objects like human bones and muscles, this added pressure is not much of a problem; but it is a problem for any air-filled spaces like the mouth, ears, paranasal sinuses and lungs. This is because the air in those spaces reduces in volume when under pressure and so does not provide those spaces with support from the higher outside pressure. Even at a depth of 8 ft (2.4 m) underwater, an inability to equalize air pressure in the middle ear with outside water pressure can cause pain, and the tympanic membrane can rupture at depths under 10 ft (3 m).