The Knock Up Stream (突き上げる海流（ノックアップ ストリーム） Nokku Appu Sutorīmu?) is a powerful pressurized water stream that shoots upwards to the sky from the bottom. The Knock Up Stream is created by a giant underwater cave filled with gas. At some point in time, the gas pressure is too big and creates a crack in the ceiling, then a giant whirlpool is created from the crack. Once most of the gas gets free, the seabed explodes, sending a giant stream upwards. This event happens only 5 times a month. The strength of each particular event varies dramatically.