In this paper, the attention on the safety of fishig vessels is focussed on the possibility of loss consequent to loss of control in waves and/or broaching-to phenomena. To this end, the set of differential equations describing the dynamics of antisymmetric motions of roll, yaw and sway is obtained with hydrodynamic derivatives estimated from manoeuvrability and geometric parameters chosen so as to correspond to the well known BSRA trawler series. An analysis of stability of these motions reveals the possibility of dangerous phenomena depending on the trim condition and on the Froude number.
