Navigation Lights & Day Shapes Basics

Printable checklist: Launch day

Navigation lights tell other boats where you are, which way you are heading and—together with daytime shapes—what you are doing. The Inland Navigation Rules in 33 CFR Part 83, Subpart C (Rules 20–31) set when lights and shapes must be shown on U.S. inland waters. The U.S. Coast Guard Boater's Guide to the Federal Requirements for Recreational Boats restates the basics for recreational operators: show lights from sunset to sunrise and in restricted visibility (fog, rain, haze), and treat a sailing vessel or human-powered craft under mechanical propulsion as a power-driven vessel. Discover Boating (NMMA) adds the practical point: test lights before you leave, keep spares, and do not let extra lights wipe out the required pattern.

We do not invent wattage, candela ratings or visibility ranges beyond the official Rule 22 tables, and we do not invent day-shape sizes beyond what the Rules and Annex I require. Carriage of the rest of your federal safety gear (PFDs, extinguishers, visual distress signals and so on) is in required safety equipment by length—this guide expands that guide's Navigation lights section rather than replacing it. Confirm state overlays in State Rules and your state page.

When lights and shapes are required (Rule 20)

From 33 CFR 83.20 (Inland Rule 20):

  • Lights apply from sunset to sunrise. During those hours, show only the prescribed lights—or other lights that cannot be mistaken for them, do not impair their visibility or distinctive character, and do not interfere with a proper lookout.
  • If you carry the prescribed lights, also show them from sunrise to sunset in restricted visibility, and you may show them whenever else you judge it necessary.
  • Day shapes apply by day.
  • Lights and shapes must meet Annex I (33 CFR part 84). You may lower lights or shapes if needed to pass under a bridge.

Discover Boating: turn lights on from sunset to sunrise and in poor visibility; know rules by boat size, type and location; inspect regularly and keep spare bulbs aboard.

What each light means (Rule 21)

Plain definitions from 33 CFR 83.21 (the arcs are part of the legal definition—not marketing copy):

Light Color / type Arc (Inland Rule 21) Recreational takeaway
Masthead light White, on the fore-and-aft centerline (as nearly as practicable under 12 m) 225° from right ahead to 22.5° abaft the beam on each side Shows you are a power-driven vessel underway (with sidelights and sternlight)
Sidelights Red port, green starboard 112.5° each, from right ahead to 22.5° abaft the beam Tell others which side they are looking at; under 20 m they may be combined in one centerline lantern
Sternlight White, as nearly as practicable at the stern 135° (67.5° from right aft each side) Shows your stern aspect
All-round light Color as required by the Rule that calls for it 360° Common recreational use: white anchor / all-round white on small power boats
Towing light Yellow, same arc as a sternlight 135° Mostly for towing configurations (Rule 24)—know it when you see it

Discover Boating: if you see both red and green on an approaching vessel, it is heading toward you.

Minimum visibility ranges (Rule 22)

33 CFR 83.22 sets minimum ranges in nautical miles. Intensity must also meet Annex I (33 CFR part 84). These are the ranges from the regulation—not manufacturer marketing claims:

Vessel length Masthead Sidelights Sternlight All-round (white/red/green/yellow)
Less than 12 m (~39.4 ft) 2 nm 1 nm 2 nm 2 nm
12 m to under 50 m 5 nm (3 nm if under 20 m) 2 nm 2 nm 2 nm
50 m or more 6 nm 3 nm 3 nm 3 nm

(Towing and special flashing lights have their own rows in Rule 22; see the regulation text.)

Power-driven vessels underway (Rule 23)

33 CFR 83.23: a power-driven vessel underway shall exhibit a masthead light forward, sidelights and a sternlight. A second masthead light abaft and higher is required at 50 m and above (optional below 50 m).

Small power boats (under 12 m): instead of separate masthead + sternlight, you may show an all-round white light and sidelights—the common recreational “sidelights + all-round white” setup.

Great Lakes: a power-driven vessel may carry an all-round white light in lieu of the second masthead light and the sternlight, in the position of the second masthead light and visible at the same minimum range (83.23(e)).

Sailboats and boats under oars (Rule 25)

33 CFR 83.25:

  • Under sail only: sidelights and a sternlight. Under 20 m, those may be combined in one lantern at or near the top of the mast.
  • Optional extra (not with the combined lantern): two all-round lights at the mast top, upper red, lower green.
  • Under 7 m sailboats: show the sailing lights if practicable; otherwise an all-round white light or a ready white torch/lantern shown in time to prevent collision.
  • Vessels under oars: same options as sailing vessels under this Rule.
  • Sail + engine at the same time: you are treated as power-driven for the Rules (Boaters Guide notice). By day, exhibit forward where best seen a conical shape, apex downward. Under 12 m that shape is not required but may be shown (83.25(e)). At night, show the power-driven light pattern (masthead or all-round white as applicable)—not sail-only lights.

USCG Boating Safety Circular guidance (and the Boaters Guide notice) underscores a common mistake: a sailboat with an auxiliary that can only switch “running lights” as a powerboat package may show the wrong pattern under sail alone. Know which switch gives sail lights vs power lights.

At anchor and aground (Rule 30)

33 CFR 83.30:

  • At anchor: where best seen, an all-round white light in the fore part or one ball by day; plus a second all-round white light at or near the stern, lower than the forward light. Vessels under 50 m may show a single all-round white where best seen instead.
  • Exemptions (anchor lights/shapes): vessels under 7 m not in or near a narrow channel, fairway, anchorage, or where other vessels normally navigate; vessels under 20 m in a Coast Guard–designated special anchorage area.
  • Aground: show the anchor lights (as applicable) and, if practicable, two all-round red lights in a vertical line and three balls in a vertical line. Vessels under 12 m are not required to show the extra aground lights/shapes in 83.30(d)(i)–(ii).

Do not show underway running lights and the anchor light at the same time—the Rules prescribe one status at a time (Boaters Guide / circular practice notes; Rule 20 limits extra lights).

Day shapes recreational boaters actually use

Shapes are the daytime counterpart to lights (Rule 20(d)). For typical recreational boats, the ones that matter most from Subpart C are:

Situation Day shape (Inland Rules) Cite
At anchor One ball (forward / where best seen; under 50 m a single all-round white replaces the two-light night pattern) 83.30(a)–(b)
Aground Three balls in a vertical line (plus anchor lights at night if practicable) 83.30(d)
Sailing vessel also under power Cone, apex downward, forward where best seen (optional under 12 m) 83.25(e)
Tow over 200 m Diamond where best seen (towing / being towed) 83.24
Constrained by draft (power-driven; uncommon for small recreational boats) Cylinder where best seen 83.28

Larger commercial patterns (fishing cones, not-under-command balls, restricted-maneuverability ball–diamond–ball, dredging signals) are in Rules 26–27. You need to recognize them; most small recreational boats are not required to display them (for example, vessels under 12 m are generally excused from Rule 27 lights/shapes except diving operations—83.27(g)).

Common mistakes

Drawn only from the Coast Guard Boaters Guide, USCG Marine Safety Alert 10-15 and Discover Boating:

  1. No lights after dark or in fog — an obvious Navigation Rules violation the Coast Guard cites in the Boaters Guide.
  2. Wrong pattern for sail vs power — under sail alone you must not look like a powerboat; under sail+power you must look (and shape) like power.
  3. Unapproved replacement lights — recreational nav lights must meet ABYC A-16 per 33 CFR 183.810. MSA 10-15: packaging should show USCG Approval 33 CFR 183.810, ABYC A-16 (or equivalent), lab, maker, model, visibility in nm, type-test date and bulb spec.
  4. Decorative / underwater / rub-rail LEDs that can be mistaken for nav lights, wash out the required character, or wreck the lookout (Rule 20). Blue LEDs that appear to flash in waves can look like the flashing blue reserved for law enforcement (33 CFR 88.05)—MSA 10-15.
  5. Skipping the pre-departure light check — Discover Boating: test before you go; keep spares.
  6. Assuming “about 2 miles” covers every light — Rule 22 gives 1 nm sidelights under 12 m; buy and mount lights that meet the table for your length.

Before you leave the dock

Nav lights belong on the same pre-launch pass as PFDs and communications: printable Launch Day checklist, first-season checklist, and cold-water readiness in cold-water safety (Alaska). If you carry a VHF, know Channel 16 and radio-check etiquette from VHF marine radio basics. Restricted-visibility electronics (radar vs AIS) are in radar basics for recreational boaters and AIS basics for recreational boaters. Book a free Vessel Safety Check with the Coast Guard Auxiliary. Budget replacement lights in the True Cost tool if you are still outfitting.

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