Wiktionary
water bomb
n. A small balloon filled with water which bursts upon being thrown at somebody.
Usage examples of "water bomb".
The water bomb's membrane snagged on some projection on the ship's hull.
The plas tic bottle slipped from her relaxing fingers, hit the floor between her sneakers, and exploded like a balloon water bomb.
Drenched and sputtering, Ron staggered sideways into Harry, just as a second water bomb dropped - narrowly missing Hermione, it burst at Harry's feet, sending a wave of cold water over his sneakers into his socks.
Drenched and spluttering, Ron staggered sideways into Harry, just as a second water bomb dropped –.