This paper describes the electrical organs of marine fish species. At the beginning, the structure of the electrical organ and electrocytes, the cells that build it, are described, as well as the method of electric organ discharge. In the continuation of the work, electric fish are divided into three categories: strongly electric fish, weak electric fish and fish that can only feel electricity, but cannot produce it. The first group, strongly electric fish, have an electrical discharge of organs strong enough to stun a prey or use it for defence. Weak electric fish have electrical organ discharge weak to stun prey and instead of it, it is used for navigation, electrolocation and electrocomunication and called active electroreception. The third category includes species that cannot generate electricity, but can sense weak bioelectric fields generated by other animals and use them to locate prey, therefore called passive electroreception. For each described category a list of characteristic marine species is given with a detailed description of the associated electrical organs. Furthermore, important scientists credited for the discovery of electrical organs were also mentioned. Finally, the application of knowledge about electrical organs in the manufacture of a battery that works on a similar principle is described.