a tracked , amphibious vehicle , provides at least two , spaced , elongated pontoons disposed generally parallel to one another . a platform structure can be supported by and structurally connects the pontoons , the platform structure including a transom and a lowermost generally horizontally extending panel . a continuous , endless belt can encircle each pontoon engaging bogie wheels on the pontoon . a supplemental , marine drive assembly includes a hydraulic motor having a shaft with an axis , a propeller shaft having an axis , wherein the motor axis and propeller axis are aligned . a universal joint connects the hydraulic motor to the transom . a housing includes a sleeve that contains the propeller shaft .