A system for lashing a tender assist drilling unit (TADU) to a floating production platform includes a plurality of winches on the forward end of the TADU, a plurality of sheaves on the upper portion of the hull of the platform, a plurality of connection devices on the lower portion of the hull of the platform, and a set of lashing lines, each of which extends from one of the winches, through a corresponding one of the sheaves, and vertically down alongside the platform hull to a corresponding one of the connection devices to which it is attached. The winches are operable to reel in and to pay out the lashing lines to control the separation distance so as to maintain an optimal operational separation distance during normal environmental conditions, while allowing the separation distance to be increased in severe conditions.