ae91fae9_trols___Official_Terraria_Wiki__Notes
[Action] Flick Left Thumbstick up [Effect] Up (Alt) [Notes] 
Allows "swimming" upwards (repeated jumping) while underwater if Flippers, Diving Gear, or Neptune's Shell is equipped as an Accessory. Activate the ability of jumping items like Spectre Boots, Sandstorm in a Bottle, etc. Toggles gravity for character (when using a Gravitation Potion).
Game controls - Official Terraria Wiki
Notes