Do you want to delay the water effect, or increase its intensity gradually? If you want to delay, then disable it on start of layout, and enable only when needed.
If you need to increase effect intensity, say from 1 to 10, use Tween behavior, "Tween Value" action. When this tween is running, set water effect parameter to Sprite.Tween("tag").value
Or you can probably change effect parameter based on the sprite opacity, something like "set effect parameter 0 to (Self.opacity/10)"