A watertaxi can reduce the travel time through the city of Rotterdam in comparison with public transport. To make estimations on the average reduced travel time within Rotterdam, a generic method is developed. This method is capable of finding locations for watertaxi jetties. To achieve this, the watertaxi, public transport, and the walking to and from the jetties is modelled as a complete undirected graph. The formulation of the Median p- Hub Location Problem is changed by adding a second type of node and allowing direct links. With a case study to Rotterdam, the method shows to be useful to find the average reduced travel time in urban areas.