Off the rugged, wave-swept coast of Taean, a treacherous marine graveyard known historically as the "Racecourse of the Sea" has yielded two newly discovered Goryeo Dynasty shipwrecks, offering an unprecedented window into 13th-century statecraft, commerce and seafaring. The National Research Institute of Maritime Cultural Heritage said Wednesday that underwater archaeologists have fully identified the wreckage of the Mado No. 5 ship and spotted the traces of a brand-new wreck, Mado No. 6, nearby. Together, the finds illuminate the sophisticated tax-grain shipping networks that once fed the Goryeo capital of Gaegyeong. The excavation of the Mado No. 5 vessel recovered 54 artifacts, including bronze vessels, rope, anchors and bundles of preserved rice straw. Most crucially, archaeologists unearthed 26 inscribed wooden tags, or "mokgan," that meticulously document the cargo's journey, according to the institute. Deciphering the texts revealed that the cargo was collected in December 1207 — the dead of winter, when freezing gales typically kept sailors ashore. Experts deduce that Mado No.