There are regular ferry services between the United Kingdom and northwestern Spain. Brittany Ferries sails from Portsmouth to Bilbao and Santander. The trip is more than 24 hours, so not practical unless you love the ocean and have some extra time on your hands. Spain’s major ferry line, Trasmediterránea, links mainland Spain (including Barcelona) with the Balearics and the Canary Islands. This ferry's fast catamaran service takes half the time of the standard ferry, but catamarans are often canceled because they can navigate only in very calm waters. Trasmediterránea and Balearia operate overnight ferries from Barcelona, Valencia, and Dénia to the islands of Mallorca, Menorca, and Ibiza. Formentera can be reached from Ibiza via Balearia and Transmapi, a local ferry company. At 7 hours, 30 minutes from Barcelona via ferry crossing, Mallorca is the closest island. Long-stretch ferries are equipped with a choice of seating options including sleepers, a restaurant, several bars, and small shopping area.
You can pick up schedules and buy tickets at the ferry ticket office in the port.