Sam Mindoro once owned an island called Pelewan, near the Phillipines, but eventually lost it to a man named Mr. Watson. Mindoro tried to frighten off Watson and his native men by posing as a sea demon. He killed or wounded several natives in his efforts. As the Sea-Devil, Mindoro wore a scary looking suit that allowed him to breathe and speak underwater. He was extremely strong, a good fighter, and skilled with throwing knives. He used a cutlass to attack his victims, and hid in an underwater cave to ambush them