The East China Sea is big. 
The East China Sea is a large sea. 

Most of the sea is shallow. The Yangtze River flows into it. This is a very big river.
Many islands are in the sea. Some islands are part of Japan. Others are near Taiwan.
People use the sea for many things. Long ago, ships went there to find whales. Now, people find gas under the water.
It is a busy place with much to see.
The East China Sea is part of the Pacific Ocean. It sits right next to East China. Many places border this sea. You can find South Korea, China, Japan, and Taiwan nearby. 
Most of the sea is not very deep. About three-fourths of it is less than 200 meters deep. The average depth is only 199 meters. The deepest part is the Okinawa Trough. It reaches a depth of 2,256 meters.
A large river flows into the sea. This is the Yangtze River. It is the largest river in the area. There are also many islands. The Ryukyu Islands are part of Japan. Taiwan is also in the south.
People use the sea in many ways. Long ago, ships went there to hunt whales. Today, people look for natural gas under the water. Some of this gas is in the Chunxiao field. This field is a busy place for many countries.
The East China Sea is a large body of water. It is a marginal sea of the Western Pacific Ocean. This sea sits directly offshore from East China. 
This sea connects to many other parts of the ocean. To the north, it opens into the Yellow Sea. An imaginary line separates the two. This line runs between Jeju Island and the Yangtze River estuary. In the northeast, the Korea Strait connects it to the Sea of Japan. To the southwest, the Taiwan Strait leads to the South China Sea. In the southeast, gaps between the Ryukyu Islands lead to the Philippine Sea. 
Most of the East China Sea is quite shallow. Almost three-fourths of the area is less than 200 meters deep. The average depth is only 199 meters. However, some parts are much deeper. The deepest part is called the Okinawa Trough. It reaches a depth of 2,256 meters. The Yangtze River is the largest river that flows into this sea. There are also many islands and reefs found here.
History shows many ways people have used this sea. Between 1849 and 1892, American whaleships cruised these waters. They were looking for right whales. Today, people look for things deep under the ocean floor. In 1995, China discovered a natural gas field called Chunxiao. This is part of a larger group of gas fields. These fields hold about 364 billion cubic feet of natural gas. Commercial work in these areas began in 2006.
Because the sea is so important, countries sometimes disagree about it. This is often about "exclusive economic zones." These are areas where a country has special rights to resources. China, Japan, Taiwan, and South Korea all have different claims. For example, China and Japan disagree about where their zones meet. There is also a dispute over Socotra Rock. This is a submerged reef where South Korea has a research station. These disagreements happen because the sea holds many valuable things.
The East China Sea is a marginal sea of the Western Pacific Ocean. It sits directly offshore from the eastern coast of China. 
This sea acts as a massive crossroads for the region. To the north, it extends into the Yellow Sea. An imaginary line separates these two areas. This line runs from the southwestern tip of South Korea's Jeju Island to the eastern tip of Qidong at the Yangtze River estuary. In the northeast, the Korea Strait connects the East China Sea to the Sea of Japan. To the southwest, the Taiwan Strait provides a path to the South China Sea. In the southeast, gaps between the Ryukyu Islands, such as the Tokara and Miyako Straits, lead to the Philippine Sea. 
The physical geography of the sea is defined by its varying depths. Most of the East China Sea is quite shallow. In fact, almost three-fourths of the sea is less than 200 meters deep. The average depth of the entire area is only 199 meters. However, the seafloor is not flat everywhere. The maximum depth is found in the Okinawa Trough. This deep section reaches a depth of 2,256 meters. The Yangtze River, also known as the Chang Jiang, is the largest river that flows into the sea.
History shows that many different groups have utilized these waters. Between 1849 and 1892, American whaleships cruised the sea. These ships were specifically searching for right whales. In more recent history, the focus has shifted from animals to natural resources. In 1995, the People's Republic of China (PRC) discovered an undersea natural gas field. This field is named the Chunxiao gas field. It is part of a larger group of fields in the Xihu Sag area. These fields include others named Canxue, Baoyunting, Duanqiao, Wuyunting, and Tianwaitian. These resources are estimated to hold 364 billion cubic feet of natural gas. Commercial operations in these fields began in 2006.
Because of these resources, the sea is a place of significant legal disagreement. Countries like China, Japan, Taiwan, and South Korea have disputes over Exclusive Economic Zones (EEZ). An EEZ is an area where a country has special rights to resources. The width of the East China Sea is only 360 nautical miles. This creates a problem because China and Japan both claim 200-nautical-mile EEZ rights. China argues for the natural prolongation of its continental shelf. They believe their shelf extends all the way to the Okinawa Trough. Japan disagrees and proposes using a Median line division instead.
These disputes often involve specific locations and structures. For example, the Chunxiao gas field is a point of tension. While the rigs are in Chinese territory, Japan believes the field connects to reserves in disputed areas. Japan seeks a share of these natural gas resources. Another notable area is Socotra Rock, also called Ieodo. This is a submerged reef in the northern part of the sea. It is a subject of a dispute between China and South Korea. South Korea has even built the Ieodo Ocean Research Station on this reef. China has objected to these activities, calling them a breach of their EEZ rights.
Today, the East China Sea remains a highly active region. It is a place of significant military and economic activity. All four bordering nations—South Korea, Japan, Taiwan, and China—conduct military exercises there. The sea is also a site of growing naval strength. For instance, China currently possesses more naval vessels in its coastal waters than the US Navy. This has led to increased naval operations by the US Indo-Pacific Command. The sea is more than just a body of water. It is a complex system of resources, borders, and international relations.
🖼️ Images & Media (3)
More to explore
✨ What else?
Related topics you might enjoy
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.