The map shows Northern Germany with all its channels, rivers and seashore. Each player picks a haven. Objective is to visit all other players havens and be home first. There is no random element - the speed is determined by the currents and the speed of the boat (which can be changed from turn to turn within certain limits). Movement is hindered by the water gates which are quite numerous along the channels. The water gates can only be passed in certain "days" (=turns) and with certain speeds.
So, to win you have to consider not only the length of the route taken, but also the timing dictated by the water gates.