[dredmorbius]

If you're in a position to be aware of an imminent attack, ramp-time is probably within reason. Power reqirements are fairly modest by military standards -- a small fireboat can pump impresive quantities of water, and since the goal in defence / obscuring is to blind (and absorb energy), a finer atomised mist would be more effective. Filter and system fouling is likely a bigger concern.

True bolt-from-the-blue attacks are rare, though possible.

The spray profile could be modified to enable sensor detection, or alternative (off-ship, buoy, balloon, drone, ...) sensor placement could enable both eyes and shields.