NOVELTY - The inland waterway tanker (1) has liquid product cargo tanks (3) that are arranged within hull. A cargo tank heating system heats liquid product within one or more cargo tanks. A water cooling circuit comprises a bypass duct that bypasses the cooling water about cooling water flow path in thermal oil circuit heat exchanger (23). The heating system comprises one or more valves (12,13) that selectively opens or closes the cooling water flow path and a bypass duct to selectively pass cooling water through thermal oil circuit heat exchanger or to bypass thermal oil circuit heat exchanger.    USE - Inland waterway tanker for transportation of liquid product e.g. crude oil and liquefied natural gas (LNG) over inland waterways.    ADVANTAGE - Since the thermal oil circuit heat exchanger is adapted to exchange heat between the cooling water from the engine and the thermal oil, the liquid product is heated in the one or more cargo tanks by heat recovered from the cooling water and thus the tanker is achieved with energy efficient, cost effective, and relatively simple to implement.    DETAILED DESCRIPTION - Inland waterway tanker has a tanker propulsion engine installation that comprises combustible fuel powered propulsion engine (6), an exhaust system (15) and a cooling water circuit (8). The cargo tank heating system comprises a thermal oil circuit heat exchanger that has a cooling water flow path and a thermal oil flow path, and exchanges heat between the cooling water and the thermal oil. The thermal oil temperature is below cooling water temperature of cooling water emerging from the propulsion engine. An INDEPENDENT CLAIM is included for method for transporting liquid product cargo over inland waterways.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of the inland waterway tanker.    Inland waterway tanker (1)    Liquid product cargo tank (3)    Fuel powered propulsion engine (6)    Cooling water circuit (8)    Bypass duct water cooling circuit (12)    Valves (13,14)    Exhaust system (15)    Thermal oil circuit heat exchanger (23)