Contemporary studies over the last ten years have demonstrated that bony fish possess nociceptors, the simple detection of potentially painful stimuli usually accompanied by a reflex withdrawal response; that these are similar to those in mammals; that they demonstrate pain-related changes in physiology and behavior that are reduced by painkillers; that they exhibit higher brain activity when painfully stimulated; and that pain is more important than showing fear or anti-predator behavior in bony fish. This review will assess the field of pain perception in aquatic species, focusing on fish and selected invertebrate groups to interpret how research findings can inform human understanding of the physiology and evolution of pain. Further, if one accepts that these animals may be capable of experiencing the negative experience of pain, then the wider implications of human use of these animals should be considered.