A water skimmer vessel has two hulls (12, 14) between which a debris collection net or basket-like catcher (22) is arranged. Hinged flaps (68) are provided at each end of the catcher and operate to allow inflow but block outflow of debris from the catcher. Each hull of the vessel is equiped with amoter covered by a guard (28). The vessel may move in either direction and is equipped with sensors (30) on each hulll for effecting the turning and reversing of the vessel upon contact with pool skimmer box inlet (206) and the vessel can be controlled to enter the dock and permit the contents of the catcher to be discharged into the current of pool water flowing into the skimmer box.