As two actions, you create a wave of water that crashes down at a point within 20 meters. Each creature in a sphere centered on that point must make a Reflex saving throw.
On a failure, it takes 3d8 bludgeoning damage, is knocked prone if it is Large or smaller, and is pushed 3 meters away from the center of the sphere if it is Large or smaller.
On a critical failure, it takes twice as much damage and is pushed 6 meters away from the center of the sphere if it is Large or smaller.
On a success, it takes half as much damage.
On a critical success, it takes no damage.
The water then spreads out across the ground in all directions, extinguishing unprotected flames in its area and within 5 meters of it, and then it vanishes.
You can increase the damage by 1d8, push each creature an additional meter, and affect a creature of a larger size for each additional mana expended.