Knock Up Stream

The Knock Up Stream (突き上げる海流 (ノックアップ ストリーム)) is a powerful pressurized water stream that shoots upwards to the sky from the bottom of the ocean. The blast is strong enough to send a ship and even one time an island straight to Skypiea. It first appeared in Chapter 236 and Episode 152.

Creation
The Knock Up Stream is created by a giant underwater cave filled with gas. At some point in time, the gas pressure is too much 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 will happen only five times a month.

Appearance
So far, the Knock Up Stream has made 2 appearances:
 * When a part of Jaya was shot towards Skypiea.
 * When the Straw Hat Pirates used it to travel to Skypiea.