Are we heading upstream or downstream?

Boaters are often uncertain about which side of a channel marker they should pass. This is because they are not sure whether they are travelling upstream or downstream.

On the road drivers cannot deviate from the structured roadway system. How a vehicle is to be driven safely is determined using marked roadways, stop signs, traffic lights and speed limits. On the water you are confronted with an expansive waterway where there are no lines to guide your passage. In addition, you’re dealing with wind, tidal changes, heightened sea states and unfamiliar marks and beacons.

It is important for Skippers to know the upstream and downstream rule so that they can identify which side of a particular channel marker to pass safely and not run aground.

Green to Green when travelling upstream. Green to Red when seas ahead.


  • A vessel travelling downstream on the river is navigating from inland towards the sea.
  • A vessel travelling upstream on a river is navigating from sea towards the inland or mountains.
  • Always maintain a good lookout, keeping to the starboard side of the channel.
  • Do not cut corners on a river bend. This is due to current flow which causes sand and silt to be deposited on the uppercurve of the river causing shallow water. The lowercurve of a bend has the deepest water.
  • Be cautious when approaching a blind right-hand bend. Another vessel maybe navigating on the wrong side. Sound one long blast to let other vessels know of your presence.
  • Port and starboard channel markers indicate where to safely navigate within the channel.
  • A port marker is coloured red and the starboard marker is coloured green.
  • When travelling upstream keep a green starboard channel marker on your starboard-side.
  • When travelling downstream keep  the green starboard channel marker on your port-side  and, a red port channel marker on your starboard side.


Driving your vessel on a river you see a channel marker. However, you are unsure which direction you are travelling upstream (in from sea) or downstream (out to sea).

Determine whether you’re travelling upstream or downstream.

  • Ask a fellow boater or locals  which direction is towards the sea?
  • Identify the buoyage direction for the area on your chart.
Look for this symbol on a chart or boating map.
  • Establish high and low tide times from a tide table of the area. This information will help you to identify which direction is up or downstream by determining the direction the current is flowing. Example: If a high tide is earlier and the tidal height is falling, then the current is travelling (downstream) out to sea. If a high is later and the tidal height is rising, then the current is then travelling (upstream) in from sea.
  • Know the characteristics of the lateral channel marks.

Once you understand this boating rule you will know what side to pass a channel mark. The upstream – downstream rule is simply explained and demonstrated on the water, during many of our training sessions.


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