<P> To avoid collisions , vessels mount navigation lights that permit other vessels to determine the type and relative angle of a vessel , and thus decide if there is a danger of collision . In general sailing vessels are required to carry a green light that shines from dead ahead to 2 points ( ​ 22 ⁄ ° ) abaft the beam on the starboard side ( the right side from the perspective of someone on board facing forward ) , a red light from dead ahead to two points abaft the beam on the port side ( left side ) and a white light that shines from astern to two points abaft the beam on both sides . Power driven vessels , in addition to these lights , must carry either one or two ( depending on length ) white masthead lights that shine from ahead to two points abaft the beam on both sides . If two masthead lights are carried then the aft one must be higher than the forward one . Hovercraft at all times and some boats operating in crowded areas may also carry a yellow flashing beacon for added visibility during day or night . </P>
<P> To avoid collisions , vessels mount navigation lights that permit other vessels to determine the type and relative angle of a vessel , and thus decide if there is a danger of collision . In general sailing vessels are required to carry a green light that shines from dead ahead to 2 points ( ​ 22 ⁄ ° ) abaft the beam on the starboard side ( the right side from the perspective of someone on board facing forward ) , a red light from dead ahead to two points abaft the beam on the port side ( left side ) and a white light that shines from astern to two points abaft the beam on both sides . Power driven vessels , in addition to these lights , must carry either one or two ( depending on length ) white masthead lights that shine from ahead to two points abaft the beam on both sides . If two masthead lights are carried then the aft one must be higher than the forward one . Hovercraft at all times and some boats operating in crowded areas may also carry a yellow flashing beacon for added visibility during day or night . </P>
where is the white light located on a boat
where is the white light located on a boat
shines from astern to two points abaft the beam on both sides
shines from astern to two points abaft the beam on both sides