From the Kingdom Hearts Wiki: A world of information not accessible by Gummiship
Water Syphon (ウォータアスピル, Wōta Asupiru?, lit. "Water Asper") is an ability in Kingdom Hearts III. It allows the user to recover their MP when Water damage is taken. The greater the damage taken, the greater the MP recovery.
In Kingdom Hearts III, Water Syphon is a support ability. It can be multi-installed to increase its effect.
Learning Water Syphon
Kingdom Hearts III