As we watched her there were signs of a struggle taking place on board--pistol-shots rang out, and a heavy form plunged over her taffrail.  Instantly several men rushed to the stern and opened fire on the object, which, so many of our crew declared, was a man swimming. This it turned out to be.  Amid a hail of shots that churned up the placid water all around him a man’s head appeared, and the swimmer, using powerful strokes, made directly towards us.