The shark is a kind of creature that we are more familiar with. It is a kind of large fish. Most sharks live in the ocean and are marine fish; They don't live in fresh water. They're not freshwater fish. However, sometimes sharks can be seen in the area where the Tamsui River flows into the sea, because the fresh water and sea water at the mouth of the sea are interlaced. Some people often refer to "freshwater sharks", but in fact this kind of fish is a fish in the class of bony fishes and catfishes, just because it looks like a shark and is called a shark, it is not a real shark, and it is not related to sharks, because sharks are fish in the class of cartilaginous fishes.
As mentioned above, most sharks live in the ocean. They are marine fish and cannot live in fresh water. This is because sharks have been living in the ocean for a long time, and have already adapted to the marine environment, their body structure and internal regulation mechanism are adapted to the marine environment. The difference between freshwater environment and seawater environment is very large, for example, the pressure and osmotic pressure in seawater are very large, but the pressure and osmotic pressure in freshwater are relatively small.
Once sharks are in fresh water, their bodies will fill with water due to changes in osmotic pressure, and at the same time, their bodies will expand due to pressure. When the pressure is balanced inside and outside, they will stop. At this time, they may die because their internal organs cannot adapt. Generally speaking, sharks can only persist in fresh water for a short period of time, not more than an hour.
