Abstract: An apparatus and method for cleaning a boat in the water without pollution. Included are a floating, water-impervious basin and a filtration system. Included are a floating, water-impervious basin and a filtration system. The basin has side walls sloped downwardly to a nadir spanning substantially the full length of the basin, an opening allowing the surrounding water to enter the basin as well as ingress and egress of boats, and a gate movable into a closed position forming a cleaning chamber in the basin. After a boat is in the chamber, the gate is closed to create a pool of water in the chamber isolated from the surrounding water and in which a boat may float while being cleaned. As the gate is closing behind a boat, it allows water to pass therethrough thereby to facilitate closure, and yet is substantially sealed when closed. The filtration system includes a collector pipe lying submerged in the nadir and a pair of return pipes that float on the water in the basin.

Abstract: A boat enclosure system for performing boat maintenance work on the water has a U-shaped floating dock forming a three sided enclosure with an opening at one end to enable boats to sail into and out of the enclosure. A bag of flexible, waterproof material is suspended around part of its periphery from the periphery of the dock to form a chamber below the dock, the remainder of the bag periphery extending across the open end of the dock so that it can be dropped into a lowered position allowing clearance below the water for boats to sail in and out of the chamber, and pulled up above the water level when a boat is in the dock to form a closed chamber below the water surface around the hull of the boat. The chamber is connected to a pump and filter unit for circulating water from the chamber through a filter and returning filtered water back to the chamber during maintenance work.