Quick ship Q

Dart is a Rover unit that can't go on water. Do you mean something else?

If you need a fast response force to deal with Duck raids, get Hunter. If you need something to deal with Ducks swarming your army, get Siren (possibly backed by Hunter, or later on Claymore if you can afford the hover switch).

Against Dagger the answer is probably much the same, although I expect Hunter to perform worse and you could also try Corsair.

Sirens, period end of story.