 Consequently, the Bangudae site has the most ancient evidence of whaling worldwide and is considered highly important not only as a first whaling representation, but also for understanding prehistoric maritime culture in the northern Pacific area.The Sayeon Dam, built from 1962 to 1965 and expanded between 1999 and 2002, helps supply Ulsan with drinking water but has caused the rocks on which the petroglyphs are carved to be flooded for about eight months of every year.This periodic flooding raises concerns of erosion and water damage of the rock-art motifs, which are considered to be masterpieces of prehistoric art and an invaluable source of prehistoric information.