When the shrimp would run on the full moon in wintertime down in South Florida, we’d head to the inlet in my friend’s old Boston Whaler Montauk, armed with headlamps and long-handled dip nets hoping to cash in. I don’t recall the exact age we started doing this, but I do remember the feeling of being on the water for the first time at night.
Objects on the shore looked like shadows, and unlit docks suddenly appeared as we slowly made our way down the canal to the inlet. The big thing though was that other boats, which would be fully visible from miles away in broad daylight, appeared to be nothing more than moving dots of light. So, from an early age, I understood the importance of being seen and knowing what you’re seeing on the water after dark. It all starts with nav lights.
Nav-Light Basics
For most people, nav lights are not even something you think about; when the sun goes down, you just hit a switch at the helm. But it’s especially important to understand the requirements and to interpret what you see on someone else’s boat at night.
Nav-light requirements are dictated both by COLREGS (International Regulations for Preventing Collisions at Sea) and, in the United States, the Inland Navigation Rules. They’re slightly different depending on the size of your boat, whether it’s commercial or recreational, and whether you’re under power or sail. Here’s what applies to most boaters who’d be reading this magazine.
Powerboats underway that are shorter than 40 feet are required to have side lights at the bow—green to starboard and red to port—as well as an all-around white light that provides 360 degrees of visibility, mounted somewhere aft of the side lights. Often you can find this mounted on a hardtop or T-top. On small boats with no hardtops, an all-around white light will typically be mounted on a removable pole that inserts into an outlet at the stern. Regardless, the all-around light must be mounted at least 39.4 inches above the side lights. The side lights need to be visible for at least 1 nautical mile, and the all-around light for at least 2 nautical miles.
Knowing the light colors and where they’re located lets you assess which part of a boat you’re looking at, as well as the direction it’s headed. If you see a red light followed by a white light in front of you, the other boat is crossing in front of you in a right-to-left direction; green followed by white indicates left-to-right. Red and green and white means it’s coming toward you, and solid white means it’s moving ahead of you in your direction. (Unless it’s a boat on the hook displaying an all-around white “anchor light.” More on that below.)
Read Next: Night-Vision Technology for Boaters
Interpreting Other Nav Lights
You might see other lights on the water that don’t match up with what you’d expect from other boats, including those of commercial traffic, as well as fixed navigation aids such as lighted buoys and channel markers. Throw in lights from piers and jetties or even cars passing onshore, and it can get confusing. Here are just a few others.
Stationary White Light: Boats at anchor in a nondesignated anchorage area are required to display a white all-around light that’s visible to others for 360 degrees around the boat.
Yellow Light: A yellow light indicates that a commercial vessel is towing or pushing a barge. If you see a yellow light—it might even look orange—on the water, steer clear. There could be a huge unlit gap between the stern light of the towing vessel and the last barge in tow. Seeing a formation of two or three vertical lights or a diamond-shaped light pattern also indicates a commercial vessel in the process of towing.
Blue Light: If you see flashing blue lights on the water, that’s law enforcement. Behave.
