Jeong Heon, curator at the National Research Institute of Maritime Heritage, observes a live video feed from a diver's helmet-mounted camera, revealing underwater findings partially buried in muddy seafloor sediment in the waters off Gunsan, North Jeolla Province, June 26. Courtesy of Korea Heritage Service

GUNSAN, North Jeolla Province — On a balmy summer morning, June 26, a scratchy radio voice echoed across a compact barge anchored in the waters off Gunsan, North Jeolla Province.

"Wooden object discovered."

The voice, punctuated by heavy breaths, emanated from four meters below the ocean's surface. In the barge's control room, a live video feed from the diver's helmet-mounted camera revealed his findings partially buried in muddy seafloor sediment.

The operator aboard swiftly responded over the radio: "Proceed with the recovery."

Half an hour later, what reached the surface with the black-clad diver was a 1.5-meter-long chunk of hardwood, riddled with holes from years — likely centuries — of marine organisms gnawing at it.

A 1.5-meter-long chunk of hardwood, riddled with holes from centuries of marine organisms gnawing at it, is brought to the surface. The object is presumed to be a component of an old vessel, according to Jeong Heon, curator at the National Research Institute of Maritime Heritage. Courtesy of Korea Heritage Service

"Based on its shape, it's presumed to be a component of an old vessel, like an oar or an anchor," noted Jeong Heon, curator at the National Research Institute of Maritime Heritage, following an initial visual examination. "After preservation treatment and a more detailed analysis, we should be able to determine its age."

In addition to the wooden ship part, the day's underwater findings included a net bag stuffed with pottery shards and an antler now covered in barnacles, potentially destined as a tribute to a kingdom.

The surprising abundance of salvaged items suggests the possibility of sunken vessels laden with even rarer artifacts resting somewhere in the vicinity. In fact, Gunsan's Seonyu Island had historically been a strategic location for maritime exchanges in East Asia, linking the southwestern coast of Korea with Japan and China.

Serving as a key stopover on the coastal route of the West Sea, the island witnessed the passage of numerous trade and cargo ships ferrying celadons and porcelain items to the capitals of the Goryeo Kingdom (918-1392) in Gaeseong and the Joseon Dynasty (1392-1910) in Hanyang, now Seoul.

Researchers from the National Research Institute of Maritime Heritage and civilian divers are jointly continuing the mission to recover ancient artifacts from the ocean's depths in the waters off Gunsan's Seonyu Island. Courtesy of Korea Heritage Service

Gim Tae-yeon, a seasoned diver who has been exploring designated underwater zones within a vast 235,000-square-meter area, climbs a barge ladder in diving gear. Courtesy of Korea Heritage Service

It is the remnants of these historical "time capsules" that the institute under the Korea Heritage Service has been on a quest to recover from the ocean's depths over the past three years.

Its operations off Seonyu Island began after a local fisherman diver reported stumbling upon pottery fragments scattered across the seabed in 2020.

Excavations from 2021 to 2023 uncovered a treasure trove of some 670 ancient artifacts — including a shard of a polished stone dagger dating back to the Bronze Age, "giwa" roof tiles from the late Baekje era (18 BCE - 660 CE), bundles of Goryeo-era celadons and Joseon "buncheong" wares (blue-green toned traditional Korean stoneware) and even Chinese porcelain items.

"The fact that these objects span such a wide range of periods — from prehistoric ages to the end of the Joseon Dynasty — demonstrates the region's historical significance as a major stopover on sea routes for centuries," said Lee Kyu-hoon, director of the institute's underwater archaeology division.

Eighty-one Goryeo-era celadon bowls and dishes are seen half-buried in the soft mud on the seabed in 2021. Courtesy of Korea Heritage Service

This is the fourth year for researchers from the state-run agency and civilian divers to jointly continue the project, with additional hopes of discovering a complete shipwreck for the first time.

From April to October, the team's schedule alternates between 10-day shifts aboard the barge and five-day breaks on land.

In teams of two, eight divers take turns exploring designated zones within a vast 235,000-square-meter area. Each dive lasts up to 50 minutes, depending on weather conditions.

Despite the relatively shallow water depth ranging from three to seven meters, the constantly shifting currents present challenges for underwater investigation. Additionally, the soft mud on the seabed, stirred up by these currents, frequently reduces visibility.

In the face of these difficulties, Gim Tae-yeon, a seasoned diver with 20 years of experience, is one central player in the ongoing mission. He was the diver who retrieved the ship's wooden component on this particular day and was responsible for finding 81 Goryeo-era celadon bowls bundled together in 2021.

"I often tell my children that discoveries like these, made by divers like myself, can reshape our country's history," he said with a smile.

"Compared to our neighboring countries, the history of Korea's underwater archaeology is relatively young. I hope the government can allocate more budget for essential equipment and barges, and recruit more divers to further enhance these efforts."

Underwater explorations near Seonyu Island from 2021 to 2023 uncovered a treasure trove of some 670 ancient artifacts dating from the Bronze Age to the end of the Joseon Dynasty. Courtesy of Korea Heritage Service