by the National Defense Board on November 17, 1964 with Pedro Nieto Antúnez as Minister of the Navy and comprised the first two submarines, later expanded to two plus and financed by law 85/65 of November 17. With an initial cost of 700 million pesetas for the first two, the third in the series rose to 1,040 million pesetas (1964). The names and numbers of the units in the series were assigned by ministerial order 218/73 of March 29. They were named after marine animals: Delfín (Dolphin), Tonina, Marsopa (Porpoise) and Narval (Narwhal), which had a certain precedent in the fleeting Foca class (Seal class) and Tiburón class (Shark class), although, with few exceptions (those mentioned above and the Peral, Monturiol, Cosme García, García de los Reyes, Mola and Sanjurjo), the submarines of the Spanish Navy used to be identified until then only by their numerals. The Delfín (S-61) was registered in the official list of the Navy on May 3, 1973 in the port of Cartagena in a ceremony attended by the then Minister of the Navy Admiral Adolfo Baturone Colombo. Throughout its operational life, the Delfín participated in several international maneuvers together with ships from other countries, for example in June 1996 it participated in the Tapón ’96 maneuvers together with the Spanish ships Príncipe de Asturias, Santa María , Numancia and Baleares , the Americans USS Grayling and USS Conolly and the Greek destroyer Formion. Between 1984 and 1988 , during their first major careening, the Delfín-class submarines underwent a modernization that fundamentally included the weapons system, to be able to launch wire-guided torpedoes and the dsm (underwater detection) system. The modernization gave a somewhat different look to the bow of the submarines, changing the bow dome (jokingly nicknamed the nose), where the sonar is located. In 1985 he mistakenly fired a torpedo at the Cartagena base. On May 27, 1989, King Juan Carlos I reviewed the fleet at a naval stop in the waters of Barcelona. In this naval parade, the Dédalo, Príncipe de Asturias, the Baleares frigates: Andalucía, Extremadura and Victoria, the corvettes Descubierta class, Diana, Vencedora and Infanta Cristina, the submarines Delfín and Marsopa participated, among others.and other smaller units; as representatives of other countries, among others, the french Foch, the Italian Giuseppe Garibaldi, the American missile cruiser USS Belknap or the Portuguese frigate Comandante Hermenegildo Capelo. In 1994 it suffered damage to the