Insurance policies in Spain are done so according to Spanish law, therefor any vessel over 6mtrs in beam or has an engine of any form, requires insurance that gives cover for third party liability cover for death, injury, or material damage to any third party, economic losses due to direct consequences of material or personal damage and damage to other vessels both with and without contact. Without insurance however you will be unable to enter any ports in Spain, this means getting your vessel in the water in the first place without insurance is impossible.