voyager; navigator
Refers to a person who travels by sea, especially on a long voyage, or one who navigates a ship.
彼は経験豊富な航海者だ。
He is an experienced voyager.
大航海時代の航海者たちは、未知の海へと旅立った。
The navigators of the Age of Discovery set out into unknown seas.
Compound of 航海 (kōkai, 'voyage, navigation') and 者 (sha, 'person'). The word is transparently derived from its components.