Entering a Mediterranean harbour from seaward you see this buoy. Which side do you leave it on?
- To starboard
- Pass astern of it
- To port
- Either side
Show the answer
C. To port
Region A: red can to port when returning.
Buoyage & lights
Every mark answers one question: where is the safe water? Learn the families of marks, how the chart describes a light, and the lights other vessels carry, and you can read a coast and its traffic by day or night.
The sides of the channel
Which side do I leave a red buoy on, coming into harbour?
To port: in IALA Region A, which covers Europe and the Mediterranean, you leave red marks to port and green to starboard coming in from sea. Going out everything swaps, and in Region B the colours are reversed.
Lateral marks stand on the edges of a channel. They are laid for a vessel coming in from the sea: that is the direction of buoyage. In IALA Region A, which covers Europe and the Mediterranean, you leave red marks to port and green marks to starboard on the way in. Going out, everything swaps.
Port handred · can · red light
Starboard handgreen · cone · green light
The shape repeats the colour: a can is port hand, a cone is starboard hand. In Region B (the Americas, Japan, Korea, the Philippines) the colours are reversed, the shapes are not. Where a channel divides, a red mark with a green band, Fl(2+1) R, tells you the main channel lies to starboard; green with a red band, to port.
Rule
Region A, entering harbour: red to port, green to starboard.
Which side of the danger is safe
Which side do I pass a north cardinal buoy on?
On its north side: a cardinal mark is named after the side where the safe water lies. Pass north of a north cardinal, east of an east, south of a south and west of a west.
A cardinal mark is named after the side on which the safe water lies: pass north of a north cardinal, east of an east cardinal. Two black cones on top say which one it is, and the black band of the pillar sits where the cones point.
NorthQ
EastQ(3)
SouthQ(6)+LFl
WestQ(9)
At night the white light counts like a clock face: three quick flashes for east, six and a long one for south, nine for west, and an unbroken quick flash for north.
Rule
The cones point to the black. Up: north. Down: south. Base to base: east. Point to point: west.
Marks that stand alone
Which side do I pass an isolated danger mark on?
Either side, but keep off it: an isolated danger mark sits on a small danger with clear water all round. A safe water mark is the opposite, deep water all round, such as the landfall buoy of a channel.
An isolated danger mark sits on a small danger with clear water all round: keep off it, pass either side. A safe water mark is the opposite: deep water all round, the landfall buoy at the start of a channel. A yellow special mark shows an area, such as a swimming zone, a cable or a racing mark, not a danger to steer by.
Isolated dangerFl(2)
Safe waterIso · Oc · LFl 10s
Specialyellow light
New wreckblue / yellow
A blue and yellow buoy marks a new wreck not yet on the chart. A new danger may also be shown by two identical marks side by side.
Reading a light off the chart
What does Fl(3) 15s 49m 22M next to a lighthouse on the chart mean?
It is the light's rhythm: a group of three flashes every 15 seconds, the light 49 metres above the sea, nominal range 22 miles. Time the light at night to tell it from its neighbours.
Every light has its own rhythm, printed beside it on the chart, so you can tell one from another by timing it. Fl(3) 15s 49m 22M reads: a group of three flashes every 15 seconds, the light 49 metres above the sea, nominal range 22 miles.
| Chart | What you see |
|---|---|
| F | Fixed: a steady light |
| Fl · LFl | Flashing, mostly dark · a long flash of 2 s or more |
| Oc | Occulting: mostly light, short eclipses |
| Iso | Equal light and dark |
| Q · VQ | Quick, about one flash a second · very quick, two |
The nominal range assumes 10 miles of visibility: in haze you see the light later. A low eye also hides it behind the horizon, and the glow you see first, the loom, is its beam sweeping the sky.
Lights that show the way in
What do I do if a sectored light at a harbour entrance turns red or green?
Steer back until it shows white: a sectored light shows white over the safe approach and red or green over the dangers on either side. Sector limits on the chart are true bearings from seaward.
A sectored light shows different colours on different bearings: white over the safe approach, red and green over the dangers on either side. If it turns red or green, steer back until it shows white. Sector limits on the chart are true bearings from seaward.
Leading lights are two lights, the rear one higher. Keep them one above the other and you are on the line. If the front light moves to one side, steer to that side to bring them together.
What another vessel's lights tell you
How do I tell a sailing yacht from a motor boat by her lights at night?
A vessel under power shows a white masthead light above her red and green sidelights; a sailing vessel shows the colours alone. A yacht motor-sailing counts as under power.
From sunset to sunrise and in poor visibility every vessel under way shows a red sidelight to port, a green one to starboard and a white sternlight. A vessel under power adds a white masthead light shining forward. So white above the colours means power, colours alone mean sail. A yacht motor-sailing is under power.
Power, bow onwhite over both sidelights
Sail, bow onsidelights, no white
Sail, tricolourthe colours at the masthead
From asternone white light, low
A sailing yacht under 20 m may carry the three colours in one tricolour lantern at the masthead instead of the deck-level lights, never both. The colours give the aspect: red is her port side, green her starboard side, both together and she is coming straight at you.
Extra lights mean keep clear
What do red over white or green over white lights on a vessel at night mean?
Red over white is a vessel fishing, green over white one trawling. They are all-round lights of a vessel that cannot keep out of your way as usual.
All-round lights one above the other mark a vessel that cannot keep out of your way as usual. With sidelights she is making way, without them she is stopped.
Trawlinggreen over white
Fishingred over white
Not under commandred over red
Restricted in ability to manoeuvrered, white, red
| Lights | Vessel |
|---|---|
| Yellow above the sternlight | Towing: the tow is astern of her |
| Three red in a line | Constrained by her draught |
| White over red | Pilot vessel on duty |
| One all-round white | At anchor, under 50 m |
Remember
Red over white, fishing at night. Green over white, trawling tonight.
Practice questions
Questions from this topic, as the app asks them. Open one to see the answer.
This mark is ahead. Where is the safe water?
- West of the mark
- South of the mark
- Either side
- North of the mark
Show the answer
D. North of the mark
North cardinal: black over yellow, both cones up.
You see this mark. Which way round do you go?
- Through the middle
- Keep clear, but you may pass on any side
- Only to the north
- Only to the east
Show the answer
B. Keep clear, but you may pass on any side
Isolated danger: black with red bands, two balls; danger right under it.
The chart shows this light on the cape. What will you see at night?
- Five flashes, then a pause
- Light on 5 s, then off 5 s
- One flash lasting 5 seconds
- One flash every 5 seconds
Show the answer
D. One flash every 5 seconds
Fl 5s: a single flash, repeated every 5 s (the period).
Light ahead: Fl WRG 4s
- White sector: the safe channel in
- Red sector: rocks to the north
- Green sector: shoal to the south
- You are heading east, towards it
The light shows green. What do you do?
- Hold course: green means safe water
- Alter to starboard until it shows white
- Alter to port until it shows white
- Stop and wait until it shows red
Show the answer
C. Alter to port until it shows white
Sectored light: you are in the green sector south of the white channel; north is to port.
At night you see these lights ahead and no others. What is it?
- A sailing vessel under sail (red over green masthead lights optional)
- A trawler
- A vessel aground
- A pilot vessel
Show the answer
A. A sailing vessel under sail (red over green masthead lights optional)
Red over green at the masthead plus sidelights is a sailing vessel.
Practise it
All 100 questions of this topic are in the app: practice by topic with the reason after every answer, your mistakes brought back, and a timed mock exam. Free, no sign-up, in the browser or in Telegram.