Regular water waves – definition of ship motions – single degree of freedom motions in regular waves – uncoupled heave, pitch and roll motions – coupled heave and pitch motions – irregular waves - description of long crested waves by 2D spectrum – ship motions in 2D irregular waves – description of short-crested sea – ship motions in 3D irregular waves – dynamic effects – deck-wetness, slamming, relative motions, sea-sickness etc. – added resistance in waves – roll stabilization