Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See page_maxonapi_getting_started_foundations_cinema_parameters.
Parameter: Color
WATERSHADER_COLOR
Parameter: U Frequency
WATERSHADER_SCALEX
Parameter: V Frequency
WATERSHADER_SCALEY
Parameter: T Frequency
WATERSHADER_FREQUENCY
Parameter: Wind
WATERSHADER_WIND