The Bohai Sea is so shallow that you can see the bottom, yet it bears half of the northern country's territory. Fishermen say it's almost gasping for breath.

The average depth of the Bohai Sea is only 18 meters, not much deeper than many swimming pools, but its seabed hides oil, ships dock along the shore, and fish and shrimp are farmed by the seaside. 130 million people rely on it for food, power generation, and transportation. Many people even see it as an inland sea, thinking it is calm, but it has long been burdened by silt, ports, and oil fields.

In 2025, the Bohai oil field produced over 40 million tons of oil and gas, accounting for nearly 40% of the country’s new offshore production. Although the number looks large, it is backed by continuous efforts to increase production by over 2 million tons each year for five consecutive years. Whenever international oil prices fluctuate, the Bohai oil field bears this responsibility. Other domestic offshore oil fields have already shown signs of fatigue, and only the Bohai oil field continues to push forward.

Tianjin Port handled 24.03 million containers last year, and nearly all cargo transportation in the north passes through here. The straight-line distance from Dalian to Yantai is only 100 kilometers, but cars need to take a detour of 1,300 kilometers. In March of this year, a report on a cross-sea passage was submitted to the National Development and Reform Commission, planning to build a 125-kilometer underwater tunnel. This way, trucks from Northeast China to the Yangtze River Delta could save six hours, but whether it will be built still depends on funding and ecological considerations.

The silt from the Yellow River has decreased to less than 300 million tons a year, but the sediment accumulated over the past century still remains. In some places, the water depth is only seven to eight meters, forcing fishermen to move to the Yellow Sea. From 2010 to 2018, coastal land reclamation was intense, reducing tidal channels by 27%. The seawater cannot clean itself, and in 2018, the state stopped land reclamation and restored 3,500 hectares of wetlands, leading to a slight improvement.

The water quality has indeed improved, with the proportion of nearshore areas rated as good reaching 83.5% in 2023. This is the result of a five-year hard-fought battle, but don’t celebrate too soon. Heavy metals and microplastics in the seabed sediment are quietly rising. In 2025, PFAS was detected in Bohai sea bass, and although the levels are low, this pollution chain has already been connected.

Interestingly, the rock cores drilled by Academician Qin Yunshan using the “Jinxing” in the 1980s are still useful today. These old data are more reliable than results obtained from new instruments, as the sedimentation rate has not changed significantly over the decades. Predicting the coastline still relies on it.

The Yangtze River Estuary and Pearl River Estuary also experience sedimentation, but their openings are large and the currents are strong. The Bohai Sea is a semi-closed dead end, requiring three to five years for self-purification, making it the most vulnerable sea area in the country. By 2026, when the new policy is implemented, the provinces of Shandong, Hebei, and Liaoning will have to pay compensation to each other based on water quality conditions—those who improve more will receive funds. This is not out of goodwill but is forcing everyone to share responsibility.

Fisherman Old Zhang mentioned that in his father’s generation, they could catch fish with a net, but now they have to sail to farther places. The electricity used by power plants, the sea cucumbers sold in supermarkets, and the exported container goods all have to pass through this sea area of the Bohai Sea. It is not a scenic spot for people to enjoy but a connection point, a functioning machine, a screw that is constantly tightened; every shrimp you eat consumes a bit of its strength.