عرفنى بنفسك: 70% of the earth's surface is covered by water, so the nickname is "Blue Earth". The seabed is about 8,000 meters deep, while the land is sometimes less than 500,000 meters deep. There are many kinds of fish and plankton living here. In winter, the temperature will drop to below 70 degrees Celsius in the Antarctic and Antarctic, and the sea surface temperature is extremely low. Most of the living creatures here can not withstand the cold weather and will temporarily migrate to shelter from the c