Navigation rules in general waters
Open water has no lanes and no traffic lights. So boats use simple shared rules (the international rules for preventing collisions at sea). Two words you need: port = left side of the boat, starboard = right side. A boat that must give way has to make a clear early move. A boat that stands on keeps its course and speed.
- Head-on (meeting): both boats turn to starboard (right) and pass port to port.
- Crossing: the boat that has the other on its starboard side gives way and should not cross in front of the other boat. A helpful thought: if you see the other boat's red side light on your right, it is your duty to give way.
- Overtaking: a boat coming up from behind, faster than the one ahead, must keep out of its way until it is passed and clear.
- Always: keep a good lookout, use a safe speed, and make your move big and early so the other boat can see it.
Sound signals in sight of each other: one short blast = I am turning to starboard; two short = turning to port; three short = engine going astern; five or more short = danger or I do not understand you.
Navigation in harbours
Harbours are crowded: fishing boats, ferries, anchored ships and small boats all work in a small space. So the rules are stricter.
- Slow speed: your wash (waves from your boat) can rock moored boats and hurt people on the quay.
- Keep to the right side of the channel and between the channel buoys. Do not cut corners. The colours of channel buoys depend on the region, so read the chart.
- Do not overtake in a narrow channel unless the other boat agrees.
- Keep clear of large ships and of boats that are anchored or tied. A big ship cannot stop or turn quickly.
- Anchor and moor only where allowed. Do not block the channel.
- Listen on the radio or watch the port signals before entering or leaving.
Navigation in designated sea areas
Some busy or narrow waters are designated (marked on charts) with special rules: traffic lanes, narrow straits, fishing zones and areas where entry is limited.
- Traffic lanes (traffic separation scheme): each direction of travel has its own lane, with a separation zone in between. Join and leave at a small angle at the ends of the lane, and keep in the lane in the right direction.
- Crossing a lane: do it as close to a right angle as possible and as quickly as safe, giving way to boats in the lane.
- Narrow channels and straits: keep to the right side, and small boats must not get in the way of big ships that can only use the channel.
- Restricted or protected areas: stay out unless allowed, for the safety of people and sea life.
Navigation on lakes, rivers and designated waters
Rivers, canals and lakes are often called inland waters. The basic idea is the same, with extra care.
- Keep to the right-hand side of the channel, near your right bank, so meeting boats pass port to port.
- Rivers have a current. A boat going with the current moves faster and is harder to stop. Take extra care at bends and bridges, and use a sound signal at blind bends.
- Lakes are open, so the open-water rules (head-on, crossing, overtaking) mostly apply. Watch for shallow water, swimmers and fishing nets.
- Local rules decide many things (speed limits, priority, no-go areas). Always check the rules posted for the water you are on.
Try it
Make two paper boats. Put them at the two ends of a long tray of water. Move them toward each other. Try it once with both going straight, then with both turning to their right. Then do a crossing: one boat comes from the right side of the other, which waits and goes behind.
Key formulas and definitions
- Port = left; starboard = right. Starboard light is green; port light is red.
- Head-on: both turn starboard. Crossing: the boat with the other on its starboard gives way. Overtaking: the overtaker keeps clear.
- Meeting time = distance between boats / (speed 1 + speed 2) when they come head-on.
- Sound: 1 short = turning right, 2 short = turning left, 3 short = going astern, 5 short = danger.
Worked examples
1. Two boats are 6 km apart and head straight at each other at 10 km/h and 20 km/h. After how many minutes would they meet if neither changed course?
Closing speed = 10 + 20 = 30 km/h. Time = 6 / 30 = 0.2 h = 12 minutes. They must turn to starboard well before this.
2. Boat X sees boat Y on its right side, crossing. Who gives way?
Boat X gives way, because it has the other boat on its starboard (right) side. Y stands on and keeps its course and speed.
3. In a harbour channel two boats meet, and both keep right. Why is this safe?
Each boat uses the right half of the channel, so they pass left side to left side with clear water between them. The same rule is used on the road in many countries, so it is easy to remember.
4. A boat must cross a traffic lane that is 400 m wide at a speed of 8 km/h, going straight across. How long is it in the lane?
8 km/h = 8000 m per 60 min = about 133 m per minute. Time = 400 / 133 = 3 minutes. A slanted crossing would be longer and risky.
Common mistakes
- Turning left to avoid a boat in a head-on meeting. Both boats must turn right, or they could turn into each other.
- Thinking the stand-on boat can do anything it likes. It keeps course and speed, but must still act to avoid a collision if the other boat does not give way.
- Making a very small turn. The move must be big and early so the other boat sees it.
- Overtaking in a narrow harbour channel without agreement.