Sea of Japan

A deep marginal sea that was once a freshwater lake/Water

The Sea of Japan (also called the East Sea by Korea) is a marginal sea bordered by Japan, Russia, North Korea, and South Korea. Covering approximately 978,000 square kilometers with a maximum depth of 3,742 meters, it is almost entirely enclosed and connected to the Pacific only through narrow straits, the largest being the Korea Strait at 200 kilometers wide. During ice ages when sea levels dropped, these straits closed completely, turning the sea into an isolated freshwater lake. The Tsushima Current brings warm water from the south, creating a temperature gradient that produces heavy snowfall on Japan's western coast, making it one of the snowiest regions on Earth at sea level.