Spectrum sharing is a new approach to solve the congestion problem in the RF spectrum. A spatial approach for spectrum sharing between a radar and a communication system was proposed, which mitigates the radar interference to communication by projecting the radar waveform onto the null space of the interference channel, between radar and communication system [1]. In this work, we extend this approach to a maritime MIMO radar which experiences a time varying interference channel due to the oscillatory motion of a ship, because of the breaking of sea/ocean waves. We model this variation by using the matrix perturbation theory and the statistical distribution of the breaking waves. This model is then used to study the impact of perturbed interference channel on the spatial approach of spectrum sharing. We use the maximum likelihood (ML) estimate of a target's angle of arrival to study the radar's performance when its waveform is projected onto the null space of the perturbed interference channel. Through our analytical and simulation results, we study the loss in the radar's performance due to the null space projection (NSP) of its waveform on the perturbed interference channel.