The instantaneous free surface contour corresponding to the
time at which each load occurs is interpolated between the wave
gauge measurements taken without the model present. It should be
noted that reflections from the model will alter the surface elevation
after the initial wave–model interaction and therefore this
surface contour does not correspond exactly to the wave impacting
the device. The first snatch load occurs as the leading edge of the
main wave crest induces a heave in the model. Fig. 11(a) and (b)
demonstrates that the model is in approximately the same location
during the first snatch load for both values of wave steepness. The
second snatch load occurred as the back edge of the main wave
crest is passing the body. After the first snatch load the mooring
retracts slightly and needs to be extended again before the second
snatch load occurs. For case ST1 this occurs near the peak of the
main wave crest. As the wave gets steeper, and the model is
displaced further from its equilibrium position in surge, the second
snatch load occurs further down the wave crest and with a greater
horizontal displacement of the model. The wave imparts less force
to the model, resulting in the observed smaller snatch load.