Many aquatic animals have sharp spines that can penetrate the skin and inflict painful wounds. The most common of these animals is the sea urchin, which can be found at almost every marine dive site. These are slow moving invertebrates that can cause injury when stepped on or accidentally touched.

Many animals have spines that inject venom. One example is the stingray, which has a venomous spine on its tail. Stingrays are not known to be aggressive, but they injure many swimmers and divers who accidentally step on them. The best prevention against stingray injuries is to shuffle your feet when walking on the sand. This scares rays away from the area before you get close enough to step on one.

Other animals with venomous spines include lionfish, coneshells, and scorpionfish. Like urchins and rays, these animals do not attack, and only cause injury when touched by divers.