Navigational lights are lights shown by the ship when the ship is moving on water. These lights serve the purpose of indicating the position of the ship , direction to which the ship is moving and thus will help the officer in watch (OOW) of other ships to check if the risk of collision exists.

There are three types of navigational lights namely,
  • Masthead Light
  • Side light
  • Stern light
All these lights are defined in the IRPCS(International Regulations for the preventing  collisions at sea.)

1.Masthead light
It is a white light placed on forward and aft centreline of the vessel which shows an unbroken light to an arc of horizon of 225 degrees .It shows the white light such that , it reaches upto 22.5 degrees abaft the beam on either side. There can be two masthead lights, one forward and one aft according to the length of the vessel.

Visibility of Masthead Lights

  • In vessels of more than 50 metres or more in length , the masthead light should be visible for 6 miles 
  • In vessels of more than 12 metres in length but less than 50 metres in length, the masthead lights should be visible for 5 miles .But here vessels lesser than 20 metres in length masthead lights should be visible for 3 miles.
  • In vessels of less than 12 metres in length , the masthead lights should be visible for 2 miles.

2.Sidelight
There are two sidelights, one on each side. A red light on the port side and a green light on the  starboard side, each showing an unbroken light over an arc of horizon of 112.5 degrees that is,22.5 degrees abaft the beam on each side. In vessels less than 20 metres in length ,the sidelights may be on fore and aft centreline combined in one lantern.

Visibility of Sidelights

  • In vessels of more than 50 metres or more in length , a sidelight should be visible for 3 miles 
  • In vessels of more than 12 metres in length but less than 50 metres in length, a Sidelight should be visible for 2 miles
  • In vessels of less than 12 metres in length , a sidelight should be visible for 1 mile.

3.Sternlight
Stern light is a light  placed at the stern of the vessel, which shows an unbroken white light over an arc of horizon 135 degrees. That is 67.5 degrees on each side from right astern.

Visibility of Stern light

  • In vessels of more than 50 metres or more in length , the Stern light should be visible for 3 miles .
  • In vessels of more than 12 metres in length but less than 50 metres in length, the Stern light should be visible for 2 miles. 
  • In vessels of less than 12 metres in length , the Stern light should be visible for 2 miles.