An exhaust cooling system of an amphibious vehicle operable in land and marine modes comprises an exhaust system to be cooled, at least one air-liquid heat exchanger, at least one liquid-liquid heat exchanger, and coolant liquid in thermal communication with the exhaust system to be cooled, the air-liquid heat exchanger(s) and/or the liquid-liquid heat exchanger(s) and heated by the exhaust system. When the amphibious vehicle is operated in land mode, the coolant liquid is cooled by the air-liquid heat exchanger(s). When the vehicle is operated in marine mode, the coolant liquid is cooled by the liquid-liquid heat exchanger(s). The air-liquid heat exchanger(s) may also be used on water. The vehicle may plane, and have retractable road wheels. The air-liquid heat exchanger(s) may be mounted at the front or rear of the vehicle, or elsewhere.