He is best remembered as the Vice-Admiral who commanded the Spanish Mediterranean fleet at the Battle of Cape Passaro against Great Britain on August 11, 1718 off the coast of Sicily. Castañeta's fleet was decisively defeated. His greatest contribution to the Spanish Navy though was in the field of ship building. He was an innovator who based his designs on science. He was at the origin of the revival of the Spanish Navy in the eighteenth century. Some of the elements he introduced were even copied by the English and Dutch. Gaztañeta married twice.