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Water gets into a fish's body through osmosis, the process in which water diffuses from a higher to a lower concentration.
水通過滲透作用進入魚兒的身體，在這一過程中，水從高濃度的地方擴散至低濃度的地方。
For example, if there is more water outside of a cell than inside, water will try to flow into the cell until there is the same concentration of water on either side of the cell's membrane. The body of a fish acts the same way, either absorbing or losing water depending on its surroundings.
比方說，如果細胞外的水多于細胞內(nèi)，水就會流入細胞內(nèi)，直到細胞膜內(nèi)外的濃度相同。魚兒的身體與細胞一樣，吸水還是失水取決于它生存的環(huán)境。
Whether a fish absorbs or loses water is based on the fact that all fish must maintain a certain amount of salt in their bodies to stay healthy. Fish that live in fresh water have a higher concentration of salt in their bodies than the surrounding water.
不管魚兒吸水還是失水，事實上，所有的魚要想保持健康其體內(nèi)就必須維持一定量的鹽分。淡水魚體內(nèi)鹽的濃度要高于周圍的水。
Consequently, water continuously flows into the fish's body to attempt to dilute the amount of salt in the fish until it is equal to the amount of salt in the surrounding water. Since fish cannot allow their salt content to be diminished, their kidneys work overtime to expel excess water in the form of urine.
因此，水就不斷地進入魚兒的體內(nèi)以稀釋鹽份，直到魚兒體內(nèi)與外界的鹽的濃度持平。因為魚兒自身無法減少體內(nèi)的鹽分，所以他們的腎就要不斷工作以將多余的水以尿液的形式排出體外。
Ocean fish have the opposite problem. Surrounded by salt water, their bodies contain a relatively lower concentration of salt than the ocean water. In this case, osmosis causes the fish to constantly lose water in order to equalize salt concentration inside and outside the fish.
海魚的問題則恰恰相反。由于被鹽水包圍，他們體內(nèi)鹽的濃度與海水相比相對較低。在這種情況下，滲透作用使得魚兒不停地失水以平衡體內(nèi)外鹽的濃度。
To partially compensate for the water loss, ocean fish actually drink water through their mouths. To get rid of the excess salt they take in by drinking seawater, they excrete some salt through cells in their gills.
為了補償失去的部分水分，海水魚通常要用嘴喝水。而為了去除喝海水帶來的多余鹽分，它們會通過腮里的細胞排出一些鹽分。
