Boat Lighting Guide: Navigation Lights, Spreader Lights & Underwater LEDs | Egret Marine

Two Reasons to Think About Boat Lighting

Marine lighting serves two very different purposes, and it helps to keep them separate in your mind:

Compliance: Navigation lights are required by law (COLREGS and US Inland Rules) whenever you operate between sunset and sunrise or in restricted visibility. Getting these wrong puts you at legal risk and, more importantly, collision risk.
Upgrade: Spreader lights, underwater LEDs, cockpit lighting, and courtesy lights improve safety, usability, and aesthetics. These are discretionary but increasingly popular.

This guide covers both — starting with what you're required to have, then moving to what you might want.

Part 1: Navigation Lights (Required)

The Rules: COLREGS and US Inland Rules

Navigation light requirements come from the International Regulations for Preventing Collisions at Sea (COLREGS), adopted in US waters as the Inland Navigation Rules. The rules specify which lights are required, their color, arc of visibility, and minimum range (visibility distance).

The US Coast Guard enforces these rules. Operating without proper navigation lights is a federal violation and can affect your insurance coverage in the event of a collision.

Required Lights by Vessel Type

Powerboats Under Way (Under 12 Meters / ~39 Feet)

Masthead/Steaming light: White, visible 225° (from dead ahead to 22.5° abaft the beam on each side), minimum 2 nautical mile range. Mounted forward, higher than sidelights.
Sidelights: Red (port/left) and green (starboard/right), each visible 112.5°, minimum 1 nautical mile range. Can be combined in a single bi-color bow light on smaller vessels.
Stern light: White, visible 135° (centered on dead astern), minimum 2 nautical mile range.

Alternative for vessels under 7 meters that cannot exhibit the above lights: A single all-around white light is permitted as a minimum.

Powerboats Under Way (12–50 Meters)

Same as above, but with higher minimum visibility ranges (masthead: 3nm, sidelights: 2nm, stern: 2nm) and the masthead light must be forward of and higher than any second masthead light.

Sailboats Under Sail Only

Sidelights (red/green) and stern light (white) — same arcs as powerboats
No masthead/steaming light (that's for power)
Optional: tri-color masthead light (combines sidelights and stern light in one unit at the masthead) — only permitted when under sail, not motor

Vessels at Anchor

Vessels under 50 meters: one all-around white anchor light, visible 2nm, displayed where it can best be seen
Vessels under 7 meters at anchor away from a fairway: no anchor light required, but recommended

LED vs. Incandescent Navigation Lights

Modern LED navigation lights have largely replaced incandescent for good reason:

Power consumption: LED draws 80–90% less current than incandescent — significant for boats running on battery power
Bulb life: LED rated for 50,000+ hours vs. 500–1,000 hours for incandescent
Vibration resistance: No filament to break
USCG compliance: Ensure any LED navigation light is USCG-certified and meets the required arc and range specifications — not all LED lights sold as "navigation lights" meet the legal standard

Navigation Light Placement Rules

Sidelights must be positioned so they cannot be seen across the bow (the red light must not be visible from the starboard side)
The masthead/steaming light must be visible over the full 225° arc without obstruction from the hull or superstructure
Stern light must be centered on the stern and visible over the full 135° arc astern
All lights must be mounted so they don't interfere with the helmsman's night vision

Part 2: Upgrade Lighting (Discretionary)

Spreader Lights and Deck Lights

Spreader lights (on sailboats) and deck/cockpit lights (on powerboats) illuminate the working deck for nighttime operations — anchoring, docking, fishing, and crew movement. Key considerations:

Color temperature: Warm white (2700–3000K) is easier on night vision than cool white (5000K+). Red deck lights preserve night vision best of all.
Beam angle: Flood (wide) for general deck illumination; spot for targeted areas like the anchor locker or cockpit.
Waterproofing: Look for IP67 or IP68 rated fixtures for any exterior installation.
Mounting: Flush mount for a clean look; surface mount for easier installation.

Important: Spreader and deck lights must not be used while underway in a way that impairs the visibility or distinctive character of your navigation lights, or dazzles other mariners. Use them at anchor or when docked.

Underwater LED Lights

Underwater LEDs have become one of the most popular boat upgrades — they look spectacular at anchor and attract baitfish (and the gamefish that follow them) at night. Here's what to know before buying:

Colors

Blue/green: The most popular for fish attraction — these wavelengths penetrate water best and attract plankton, which attracts baitfish, which attracts gamefish. Green tends to outperform blue in murky water; blue is better in clear water.
White: Brightest and most visible, good for illuminating the swim platform and surrounding water for safety.
RGB/multi-color: Changeable color via controller. Maximum flexibility but more complex installation.

Mounting Options

Thru-hull: Installed through a hole in the hull below the waterline. Permanent, clean installation, best light output. Requires hauling the boat or working in the water.
Transom mount: Mounts on the transom at or just below the waterline. Easier installation, no hull penetration required. Good for most powerboats.
Drain plug mount: Replaces the existing drain plug. Easiest installation — no drilling required. Limited to one central location.
Portable/suction cup: Temporary, no installation. Good for trying underwater lighting before committing to a permanent install.

Wattage and Output

More watts = more light output and more current draw. For most recreational boats, 10–30W per light is adequate. Larger vessels or those wanting maximum fish attraction may use 50W+ units.

Installation Tips for Underwater Lights

Use marine-grade tinned wire and waterproof connectors rated for submersion
Apply marine sealant (3M 4200 or 5200) around any hull penetration — 5200 for permanent installations, 4200 if you may want to remove the light later
Run wiring through the bilge and up to a dedicated fused circuit at the fuse block
Install an inline waterproof switch or connect to your helm switch panel
Check local regulations — some areas restrict underwater lighting colors or use near certain habitats

Courtesy Lights and Interior Lighting

LED courtesy lights (step lights, under-gunwale lights, and cabin lights) improve safety and usability at anchor and at the dock:

Use red or amber LED courtesy lights in the cockpit to preserve night vision
Install step lights at companionway stairs and cockpit entry points to prevent trips in the dark
LED strip lights in the cabin draw minimal current and provide excellent ambient lighting

Wiring Best Practices for Marine Lighting

Use marine-grade tinned copper wire — not automotive wire
Fuse every circuit close to the power source
Use waterproof connectors for any exterior or bilge wiring
Route wiring away from heat sources and sharp edges; protect with grommets at bulkhead penetrations
Connect navigation lights to a dedicated, always-accessible circuit — not buried behind other switches

See our Electrical - Fuse Blocks & Fuses and Electrical - Wire Management collections for wiring supplies.

Quick Reference: Navigation Light Arcs

Light	Color	Arc	Min. Range (<12m)
Masthead/Steaming	White	225° (ahead + sides)	2nm
Port Sidelight	Red	112.5° (port side)	1nm
Starboard Sidelight	Green	112.5° (starboard side)	1nm
Stern	White	135° (astern)	2nm
Anchor (all-around)	White	360°	2nm

Shop Marine Lighting at Egret Marine

Browse our full Lighting collection for navigation lights, spreader lights, underwater LEDs, courtesy lights, and searchlights. Whether you're replacing a failed nav light or planning a full lighting upgrade, we have the right products for your boat.

Questions about navigation light compliance or lighting upgrades for your boat? Contact the Egret Marine team — we're here to help.

Boat Lighting Guide: Navigation Lights, Spreader Lights, and Underwater LEDs Explained