Lake Motosu (本栖湖?, Motosu-ko) is the westernmost of the Fuji Five Lakes and located in southern Yamanashi Prefecture near Mount Fuji, Japan.It is the third-largest of the Fuji Five Lakes in terms of surface area, and is the deepest, with a maximum water depth of 121.6 metres (399 feet), making it the ninth-deepest lake in Japan.[1] Its surface elevation of 900 metres (3,000 feet) is the same as for Lake Shoji and Lake Sai, confirming that these three lakes were originally a single lake, which was divided by an enormous lava flow from Mount Fuji.[2] The remnants of the lava flow are now under the Aokigahara Jukai Forest, and there is evidence to indicate that these three lakes remain connected by underground waterways.[1] The temperature of the water never drops below 4 °C (39 °F), making it the only one of the Fuji Five Lakes that does not freeze in winter.