Diving Essay

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Diving Although a number of human activities are conducted underwater, such as research, scuba diving for work or recreation, or even underwater warfare with submarines, this very extensive environment on Earth is hostile to humans in many ways and is therefore little explored. An immediate obstacle to human activity underwater is the fact that human lungs cannot naturally function in this environment. Unlike the gills of fish, human lungs are adapted to the exchange of gases at atmospheric pressure, not liquids. Aside from simply having insufficient musculature to rapidly move water in and out of the lungs, a more significant problem faces all air-breathing animals, such as mammals and birds. The problem is that water contains so little dissolved oxygen compared with atmospheric air. Air is around 21% O2; water typically is less than 0.001% dissolved oxygen. Elephant seals spend upwards of 80% of their lives in the ocean. They can hold their breath for more than 100 minutes, longer than any other non-cetacean mammal. Elephant seals dive to 1550 m beneath the ocean's surface (the deepest recorded dive of an elephant seal is 2,388 metres (7,835 ft) by a southern elephant seal). The average depth of their dives is about 300 to 600 metres (2,000 ft), typically for around 20 minutes for females and 60 minutes for males, as they search for their favorite foods. Sperm whales, along with bottlenose whales, and elephant seals, are the deepest-diving mammals. Sperm whales are believed to be able to reach 3 kilometres (1.9 mi) and remain submerged for 90 minutes. More typical dives are around 400 metres (1,300 ft) and last 35 minutes in duration. Myoglobin, which stores oxygen in muscle tissue, is much more abundant in these animals than in terrestrial animals. The blood has a high red blood cell density, which contain oxygen-carrying hemoglobin. The oxygenated

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