The Cantabrian Maritime Museum is a museum and aquarium dedicated to the dissemination of maritime heritage located on the edge of the bay. Its collections, one of the most important and complete in the country, allow a global approach to marine biodiversity and the various forms of relationship with it of the people of the Cantabrian Sea through the centuries and multiple points of view.

Its collections began to be formed in the 18th century, later enriched by such distinguished groups as the Institución Libre de Enseñanza, the Escuela de Náutica de Santander, the Museo del Real Astillero de Guarnizo, the Instituto Español de Oceanografía and the Centro de Estudios Montañeses.

The museum currently has an exhibition programme divided into four main sections: Life at sea, Fishermen and fisheries, The Bay of Biscay and the sea in history and Technological avant-garde facing the sea.

In 1886, the Maritime Station of Experimental Zoology and Botany was created by royal decree, which in 1889 was installed in Santander and was the first predecessor of the current museum. In 1948, the Museum of the Royal Shipyard of Guarnizo was founded, the second museum precedent. The current museum was built between 1976 and 1978, and was taken over by the Provincial Council of Santander in 1982, having been inaugurated in 1981.

The building, museum and aquarium, is the work of the architects Vicente Roig Forner and Ángel Hernández Morales. It was built between 1975 and 1978. It consists of two buildings with an exposed reinforced concrete structure, formerly joined by a canopy that was demolished during the restoration work carried out between 1999 and 2003. Its three storeys are arranged around a central covered courtyard. It had a total area of 2,200 square metres.

In 1999 it was extended by the architect José María Páez, who designed a new block attached to what had already been built. With this new building, the museum now covers an area of 8,500 square metres.