Side Lights

What Are Marine Side Lights?

Marine side lights — also called sidelights or bow lights — are one of the most critical components of any vessel's navigation lighting system. A red sidelight is mounted on the port (left) side of the boat, while a green sidelight marks the starboard (right) side. Together, they communicate your vessel's heading and orientation to other mariners, allowing them to take the appropriate action to avoid a collision.

According to the International Rules of the Road (COLREGS) and the U.S. Coast Guard regulations, sidelights must each show an unbroken arc of light spanning 112.5° — from dead ahead to just aft of the beam on their respective sides. This means that when another boater sees both red and green lights on an approaching vessel, they know it's heading directly toward them. When only one color is visible, it tells them the relative angle and side of your boat.

Why Side Lights Matter

Boating at night or in reduced visibility — fog, heavy rain, or haze — dramatically increases the risk of collision. Side lights are a legal requirement for virtually all recreational vessels operating between sunset and sunrise, and they serve as the primary tool other boaters use to gauge your direction, speed, and intentions.

Beyond legal compliance, properly functioning sidelights are a fundamental safety investment. As any experienced skipper knows, being clearly visible and predictable to other vessels is one of the best ways to prevent accidents on the water. USCG visibility requirements vary by vessel length: boats under 12 meters (39.4 ft) need sidelights visible at 1 nautical mile, while larger vessels must meet a 2-nautical-mile standard.

What to Look for When Shopping Side Lights

• USCG/COLREG Compliance: Always confirm the light meets the applicable standard for your vessel's size and operating waters.
• LED vs. Incandescent: LED sidelights are brighter, consume far less power, and have a much longer service life than traditional incandescent bulbs — a meaningful advantage for boats on 12V systems.
• Construction Materials: Look for corrosion-resistant housings such as 304 or 316 stainless steel, chrome-plated brass, or marine-grade polycarbonate that can withstand salt spray, UV exposure, and vibration.
• Mount Style: Side lights come in side-mount, top-mount, and combination bow light configurations. Match the mount style to your hull design and existing mounting points.
• Waterproof Rating: For permanent installations, an IP67 rating ensures the light remains sealed against water intrusion even in rough conditions.

Top Brands in Marine Side Lights

Sea-Dog Line is a respected name in marine hardware, offering a broad range of USCG-compliant sidelights built from corrosion-resistant stainless steel. Their LED side-mount and top-mount navigation lights are popular with power boaters and sailors alike for their rugged build quality and straightforward installation.

Seachoice is known for delivering quality marine accessories and OEM replacement parts at an accessible price point, making their sidelights a go-to choice for boaters who want reliable, regulation-compliant lighting on sail or powerboats under 39 feet without overspending.

Attwood Marine is a long-established marine accessories brand with one of the widest selections of navigation lighting in the industry. Their sidelight lineup spans everything from compact deck-mount bow lights to fully featured LED upgrade kits, giving boaters of all vessel sizes a reliable option that meets USCG standards.