The scale and age of extreme hydrological events that have been manifested over the past 2000 years on the coast of Valentin Bay is established based on stratigraphic study and radiocarbon dating of different facies deposits. The deposits of four major historical tsunamis (1993, 1983, 1644, and the 12th century) and a paleo-tsunami, which occurred between 1700–1800 cal yr BP. BP, were found. Sedimentation zones were mapped. The composition of diatoms in tsunami sands has been studied in detail. Along with marine and brackish water species tsunami waves also carried most freshwater forms that were redeposited from the coastal lake. Much of the material was supplied from depths up to 5 m. The correlation of events with data for the Japanese Islands is carried out. It has been suggested that the most dangerous tsunamis for this part of the Eastern Primorye coast are caused by submarine earthquakes with epicenters located near the Okushiri Island. The tsunamis associated with earthquakes with epicenters located near the northwestern Honshu Island, were less pronounced. Data on the irregular frequency of extreme floods during the last millennium has been obtained. It was established that the pluvial phase of the Warm Medieval Period ended in the early to mid-12th century. During the Little Ice Age, the water content of the rivers was insignificant, only two events, comparable to the catastrophic floods of the late 20th to early 21st century, are known to correspond to the warm phase of the mid-14th century to early 15th century. Only two of the modern floods have left traces recorded in the sedimentary sequences of the Valentin Bay coast.