Like the Air Sweeper, the Water Cannon will be a deterrent to ground troops that end up in its attack range.
The Water Cannon will shoot strong bursts of water at a single target or group of targets causing a puddle to form around the target that will reduce movement speed for troops that are within it and troops that walk onto the puddle. The upgrades to the Water Cannon can either increase the size of the puddle to engulf a wider area, cause greater movement reduction or take longer for the puddle to dissipate. The water cannon is not designed to reduce health.
This defensive structure will have an unlimited amount of water supply which it will source from sea.
This defensive structure will work well against troops that are grouped together such as Hogs, Valks and other light spammable troops. Heavy troops will be affected to a much lesser extent such as the Pekka and Golem. Puddles will still form around these heavy troops and any lightweight troops that fall victim to it will suffer the penalty.
Edit: Another good change in game which I didn't realize until PokeManiac mentioned it below.
Unlockable at TH8 or 9? There will be a maximum of 2. The second structure may not be unlockable until TH9 or 10.This might also emphasize Haste spell usage even more !!



