If you get confused over the rules and regulations of the sea, and can't tell the difference between variation and deviation, Robert Avis offers some expert advice that will help you steer clear of hot water.

If you get confused over the rules and regulations of the sea, and can’t tell the difference between variation and deviation, Robert Avis offers some expert advice that will help you steer clear of hot water.

(November 1997)

The basics of the International Regulations for Preventing Collisions at Sea derive from the position of another vessel relative to your own.

Rule 1. If your boat has navigation lights, the relative positions follow the arcs of the lights.

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Rule 2. So, in reality, the power-driven vessel that has another on her starboard bow shall give way to starboard, passing around the other’s stern (see Rules 15-17 on the next page).

If changing to starboard, it may be appropriate to give one short blast (“I am altering my course to starboard”). However, if the give-way vessel doesn’t give way, the stand-on vessel is obliged to give way to starboard, slow down or stop when it becomes apparent that the only way to avoid a collision is to take action herself.

Normally, the sounding of five or more short blasts is recommended to show that the movements of the give-way vessel are not understood (or words to that effect!)

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Rule 3. When two power-driven vessels meet head on, they should both alter to starboard and pass each down the other’s port side (see Rule 14 on the next page).

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Rule 4. When any sort of vessel (even a sailing vessel) overtakes another, she should give way until she is past and clear. She may alter either to port or starboard, and what determines past and clear will be depend on the circumstances of the situation. The vessel being overtaken should maintain her course and speed