Section I: Conduct of vessels in any condition of visibility
Look-out at sea: Rule 5
In practice
- A look-out is more than watching ahead of the bow: it covers sight, hearing, radar and every other means available in the situation.
- AIS can supplement the picture, but it replaces neither visual nor radar observation, and it is not a basis for collision-avoidance decisions on its own.
- "At all times" means without gaps. Chart work, equipment or paperwork must not cost you the situational awareness.
Text of Rule 5: Look-out
Every vessel shall at all times maintain a proper look-out by sight and hearing as well as by all available means appropriate in the prevailing circumstances and conditions so as to make a full appraisal of the situation and of the risk of collision.
Text of the International Regulations as amended, quoted from the consolidated U.S. Coast Guard Navigation Rules (public domain); spelling follows the IMO original. When in doubt, the Convention decides.
The common mistake
Limiting the look-out to the sector ahead of the bow. A proper look-out covers the whole horizon, including the sectors abaft the beam and astern.