Anchored
Rule 30(a)
One ball
A vessel at anchor exhibits one black ball forward where it can best be seen.
ColRegs Day Shapes
The shapes vessels exhibit during the day to signal their status — balls, diamonds, cones, and cylinders, hoisted in specific arrangements. Required by the International Regulations for Preventing Collisions at Sea (ColRegs), Part C. Rotate the observer angle below to see how silhouettes change with viewing direction.
Interactive trainer
Drag the slider to rotate around the vessel. Switch to quiz mode to test yourself — the caption hides and you pick the vessel from the chips.
Study mode
Vessel at anchor
Ahead (0°)
AheadStbdAsternPortAhead
Reference catalogue
Not under command
Rule 27(a)
Two balls in a vertical line
A vessel unable to manoeuvre as required by the Rules due to exceptional circumstance (steering failure, engine breakdown).
Restricted in ability to manoeuvre
Rule 27(b)
Ball — diamond — ball, vertical line
A vessel whose nature of work restricts her ability to manoeuvre as required (cable-laying, surveying, replenishment at sea).
Aground
Rule 30(d)
Three balls in a vertical line
A vessel aground also exhibits the lights of an anchored vessel at night. The three balls warn approaching traffic she cannot move.
Fishing (not trawling)
Rule 26(c)
Two cones, points together (apex-to-apex)
A vessel engaged in fishing with gear other than trawls. If outlying gear extends >150m horizontally, an additional cone points toward the gear.
Trawling
Rule 26(b)
Two cones, points together
Same vertical signal as fishing — point-to-point cones. The lights at night differ (green over white) but the day shape is identical.
Towing — length of tow >200m
Rule 24(a)
Diamond
Exhibited by both the towing vessel and the vessel being towed when the tow length exceeds 200 metres.
Constrained by draft
Rule 28
Cylinder
A power-driven vessel which, because of her draft in relation to the available depth and width of navigable water, is severely restricted in her ability to deviate from the course she is following.
Sailing vessel under engine
Rule 25(e)
Cone, apex downward
A sailing vessel proceeding under sail and also being propelled by machinery shall exhibit forward a conical shape, apex downward. She is treated as a power-driven vessel under the Rules.
Mine clearance
Rule 27(f)
Three balls in a triangle
A vessel engaged in mine clearance operations. The triangle of three balls (one at the mast and one at the end of each fore yard-arm) warns other vessels to keep at least 1000m clear.
Test yourself
Take the day-shapes quiz to practise identifying vessels from their ColRegs signals.
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