It doesn't have to be exotic, a remington 870 and buckshot for each sailor should be able to keep the ship secure. When they've moved through the danger zone then have them drop off the weapons at the ship stationed at the other end.
The Pirates have AK47's and RPG's; Shotguns and buck shot are not going to cut it..
With tankers and bulk LPG carriers, I could imagine the crew would be extremely nervous at the thought of an RPG hitting the ship anywhere..With the smaller tramp steamers, a couple of RPG rounds in the hull is likely to seriously compromise its sea worthiness..
So i would think that very vunerable ships like tankers should be escorted through the area, whether by the worlds Navies or private secuirty company's wouldn't really matter.
Other craft could be armed, but it would have to be with at least .50 cal machine guns ie something that can deal with the Pirates before they get too close...
