Section 21(a) in Prevention Of Collision On National Waterways Regulations, 2002
(a)"Masthead light" means a white light placed over the fore and aft centerline of the vessel showing an unbroken light over an arc of the horizon of 22.5 degrees and so fixed as to show the light from right ahead to 22.5 degrees abaft the beam on either side of the vessel. This light shall be placed as far as practicable at height above the hull of not less than 3 metres for vessels of 20 metres or more in length and 2 metres for vessels of less than 20 metres in length.
