The electrosense of weakly electric fish is the ability to sense electric fields in water. These fish can sense electric fields generated by living creatures moving in the water (e.g., prey, predators): this is known as the passive electrosense. They can also sense perturbations of their self-generated electric field: this is known as the active electrosense and this is what we study in the laboratory. An excellent introduction to the electrosensory system can be found here