Tradition says that it was a sow that suffered from rheumatism and that was having a lot of difficulty walking, she used to go with great effort to a certain place on the shore of the Playa de los Barcos, where she wallowed in the hot waters that flowed there. After some time, the animal was completely cured. This is the origin of these baths, at least this is the popular justification for their being called Baños de la Marrana. 

These baths were opened to the public on May 2, 1901, by Dr. Vera. 

The baths consist of two construction phases: an earlier one, dating from the end of the 19th century and the beginning of the 20th century, and a second, more modern one, carried out as a result of a series of reforms after the Civil War, in which bathtubs and internal partitions were built. The Isla Plana thermal baths were abandoned in the mid-20th century.