The Port of Singapore Authority (PSA) is one of the busiest and most efficient port in the world. With about 300 vessels calling at Singapore everyday, a fast and efficient allocation of marine resources to assist the vessels in navigating in the port waters is essential in maintaining its lead and competitive edge over other ports. Scheduling these marine resources, such as pilots and tugs, is a complex task requiring the consideration of numerous constraints and factors. The olden days of manual planning using pen and paper was erroneous, uncoordinated, and slow in coping with the rapid increase in the vessel traffic. This paper describes an expert system that uses heuristics to assist human planners in the scheduling of pilots and tugs to service the vessels in Singapore.