Water Bomb

From the Super Mario Wiki

Water Bomb is the Offensive Power Shot used by Koopa Troopa in Mario Power Tennis. Rather like the Boo Blast, it involves Koopa filling up his racket with water and then hitting the ball. This shot is similar to a zero degree drop shot, making it hard to return.

Offensive Power Shots Mario Iron Hammer Bowser Fire Breath Luigi Squeaky Mallet Bowser Jr. Magic Paint Princess Peach Super Peach Spin Boo Boo Blast Princess Daisy Wonder Flower Fly Guy Tornado Twist Wario Thunder Cast Shot Diddy Kong Acrobatic Banana Waluigi Whirluigi Paratroopa Energy Ball Yoshi Rainbow Flutter Wiggler Anger Management DK Barrel Cannon Blast Petey Piranha Sludge Racket Shy Guy Lightning Spear Koopa Troopa Water Bomb

Defensive Power Shots Mario Spin Jump Return Bowser Spinning Shell Dash Luigi Poltergust Return Bowser Jr. Rolling Brush Return Princess Peach Sweet Kiss Return Boo Boo Brigade Return Princess Daisy Flowerbed Return Fly Guy Tornado Return Wario Ultra-Hand Return Diddy Kong Barrel Jet Waluigi Swimming Return Paratroopa Sky Dive Yoshi Rolling Egg Return Wiggler Flutter Return DK Boomerang Banana Return Petey Piranha Piranha Swingback Shy Guy Spear Dance Return Koopa Troopa Water Shell Dash