Traditionally, the dominant part of merchant ship maneuvering investigations is related to the 3DOF motion in horizontal plane while the roll motions during maneuvers are neglected. Nowadays, many ships like container carriers with high deck load or ferry vessels with well developed superstructures have relatively small value of transverse metacentric height. This design peculiarity reflects into ... [Show full abstract] large roll angles when ship is turning. If maneuver is performed in shallow water, besides the changes in ship stability of motion, the effective ship draft to water depth ratio is reduced eroding safety UKC clearance. In the frame of ITTC workshop SIMMAN'2008 cooperative program a container vessel model KCS was tested at BSHC in free-sailing mode. In the paper, the results of additional extensive experimental investigations of shallow water effect as well as of variation in GM value on KCS standard maneuver parameters are presented. Included is an analysis of combined contribution of both effects in ship course stability and safety.