Contrary to popular opinion, the knives we carry underwater are not for doing battle with the creatures of the deep. Still, carrying a sharp, easily accessible dive knife is a critical piece of equipment to ensure dive safety. Dive sites can have unexpected hazards such as fishing lines, nets, and kelp that can entangle and trap a diver underwater. A good knife will make quick work of dangers such as these. Knives may come with a sharpened end for piercing objects while others have flat ends that work as a screwdriver in a pinch.