Before you take a fascinating journey through the sea floor should be available shortly with the unusual human aqueous medium, in which he must plunge. What is unusual aquatic environment and how it differs from the usual for us to air? Perhaps the most important property of water, distinguishing it from the air, a high density. If the person being on the ground (at the bottom of the ocean air) under pressure of 1 kg/cm2, it is enough to plunge him into the water to a depth of only 10 m, the pressure was doubled to 2 kg/cm2. Water at 775 times denser and, hence, heavier than air.
The density of water varies slightly under the influence of temperature. So, at 20. ° C the density of water by only 0.2% compared with its density at 4 ° C. In the underwater sport water density changes do not take into account and make it equal to unity.
The density of water reminds of itself with each dive. Athlete under the water has no such freedom of movement, as in the air. His movements become smoother and slower. Sudden and rapid movements require great effort. Each area of the body diver experiencing water resistance. This resistance is greater, the higher the rate and extent of the moving body part. Therefore, floating and moving under water, it is necessary to choose such a body position relative to the path of movement and to produce such movements, which are most effective and least-cost muscle energy. All useful when navigating the movement must be performed quickly (but not sharp). This increases the reliance on water, and the preparatory movements must be performed slowly and smoothly, which greatly reduces the inhibitory effect of water.
The density of water provides the diver a state of near weightlessness. Enough to make some movements with his hands or feet to change the position of the body and start sliding, diving or surfacing. This feeling of "floating" in water is very common for swimming in the sports equipment.
Water resistance is significantly increased in the flow. When strong currents in rivers and straits, the rate can reach 2-3 m / sec or more, swimming under water and the movement is very difficult. The strength of flow may include swimmer away from the dive site, remove it from the end of the trigger and cause an accident. Therefore, before training in scuba diving should determine the speed and direction of flow, paying particular attention to the undercurrent that is unnoticed from the surface. |
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