Ship's hit points (and defense numbers) that are at 0.5 will display as zero in the battle viewer. Thus it can look like your ship should be dead, but it is still alive until one more hit occurs.
For defenses, you can tell the difference between having 0.5 defense left and 0 defense left by seeing if the zero diplayed is a white zero or a grayed out zero. The grayed out zero is a real zero meaning you are going to start taking hit point damage with the next hit.
