Bo is the Master Mariner of the world, ruler of the seas and all the craft that float on it. He is one of three beings to whom all other immortals are subject, the others being Ak the Master Woodsman and Kern the Master Husbandman. These three see everything and know more than the sons of men.
Kern was part of the Council of Immortals that bestowed upon Santa Claus the Mantle of Immortality. (The Life and Adventures of Santa Claus). In the 2000 adaptation of the story, Bo serves as a skeptical voice at the council meeting, similar to the role the King of the Wind Demons played in the Rankin Bass version.