Results of an experimental study of ship shadow effects are presented. Spectral upwelling and downwelling irradiance, and upwelling radiance were measured at 2 distances from the ship on an overcast day and sunny day. On the clear sky day it was found that while the apparent properties and derived properties of reflectance showed only negligible affects, the derived diffuse attenuation coefficients varied measurably. On the overcast day the apparent properties varied, with Ed showing the most variation. All of the derived properties on this day exhibited large variations (on the order of 40%) between casts at 0 and 9 meters.