Abstract: A bottom well and sea water piping system for vessels with which system the supply of sea water is provided for a vessel for engine cooling and other uses. The invention has only one bottom well preferably arranged on the vessel's middle line, and that the sea water piping as a whole is on the delivery side of submersible pumps. All the openings and lead-throughs of the bottom well are above the water level, most preferably on a covering plate. The sea water piping system is regulated by a heat regulating valve and a pressure regulating valve. The flow is regulated with an operating speed regulator for the motors of the submersible pumps by means of a frequency converter.