Cherbourg, France
Saint-Vaast-la-Hougue has a very beautiful and special marina. In contrast to other ports, that run dry, this one has watertight (well, more or less) locks that close when the tide goes down. The water stays in the port and so the marina of Saint-Vaast-la-Hougue is rather popular by sailing boats that make a tour along the Cotentin peninsula's coastline. This means that, when your locked in, there's no sailing out until the next high tide. Those who come too late, lay outside in the mud.