Increasingly, energy generation facilities (i.e., wave and wind) are being sited in offshore marine waters. The electricity generated from these facilities is transmitted to shore through cables carrying alternating (AC) or direct (DC) current. If DC is used, it is converted to AC for the North American grid at onshore stations. While these currents produce both electric and magnetic fields, only the magnetic field, here called an electromagnetic field (EMF), is emitted from the cable. Some marine vertebrates and invertebrates can detect EMFs (summarized in Normandeau et al. 2011). However, while it is clear that organisms can detect EMFs, less well understood is how these animals respond behaviorally to this stimulus, and concerns have been raised regarding how these organisms might interact with energized subsea cables. Among fishes, a few field or quasi-field studies have produced what appear to be minor or equivocal responses. For instance, in a study of three species of elasmobranchs held in offshore mesocosms and subjected to EMF, there were some statistically significant differences in behavior; however these differences were inconsistent among individuals within a species. In other studies, migrating European eels (Anguilla anguilla) in the Baltic Sea slowed, but did not halt, their swimming speed around an energized cable (Westerberg and Lagenfelt, 2008), and the movement of a number of fish species did not appear to be affected by an energized cable off Denmark. Along the Pacific Coast of the United States, fishers have also raised this issue; one of the specific issues is how crabs (which form major fisheries along the Pacific Coast) might respond to energized power cables. There have been few studies on the behavioral changes that invertebrates might show in the presence of EMF although a small laboratory study implied that Dungeness crabs (Metacarcinus magister) were attracted to a zone of high EMF and that crabs in some zones with elevated EMF levels were somewhat more active than control animals. Needed are studies that address how organisms respond to an in situ energized submarine power cable. The presence of energized and unenergized AC submarine cables in close proximity to one another off the coast of southern California allowed us to conduct such an experiment on crabs.