The East Sea is a marginal sea of the Pacific Ocean and is surrounded by the northeastern part of Asian Continent, the Korean peninsula, the Littoral Province of Russia, Sakhalin, and the Japanese islands. It has an area of 1,007,300㎢ approximately and has the maximum south-to-north and east-to-west distances of 1,700 and 1,100㎞ respectively.

The East Sea is an ocean basin formed by a depression of land from a huge block faulting. It is connected to the Pacific Ocean through the Tugaru Strait, to the East China Sea through the Korea Strait, and to the Okhotsk Sea through the La Perouse Strait.

The area of continental shelf is about 210,000㎢, which is approximately one fifth of the whole area of East Sea. The area of deep sea exceeding 3,000m in depth is approximately 300,000㎢, and deepest place is located near the Ogusiri Island, which is located on the northeastern part of the East Sea and has a depth of 3,762m. The average depth of the East Sea is 1,684m. On the whole, the northern and western parts are deeper than the southern and eastern parts, respectively.