What Do Green & Red Lights Mean On A Boat?

‍If you’ve ever looked out at the sea at night, you’ve probably noticed the red and green lights on all of the boats that pass by, but what do they mean?

These red and green lights help show the position of a boat in the water with the red light showing the boat’s port, or left side, and the green light showing the starboard, or right side. These lights are called side lights and they are just one type of navigation light that boats use.

Though they might not seem very significant to the average person, a boat’s navigation lights are incredibly important and can convey all sorts of information to other boaters that help to keep everyone safe when out on the water. Though it might seem complicated at first, memorizing what these different lights mean is a lot easier than you might think. So what do these red and green lights mean and what other navigation lights do boats use?

‍Common Boating Terms

Before we get into the details of what all of these different lights mean, it will be helpful to know a few common boating terms. Using directional terms like bow, stern, starboard, and port that doesn’t depend on which way a sailor is facing helps prevent miscommunication so knowing the words that are used is necessary to understand where these lights are located and what information they convey.

Bow

The front of a boat is called the bow. This part of the vessel is always pointing in the direction of where it is going and is normally pointed in shape in order to reduce water and air resistance when cutting through the water.

The name bow most likely comes from medieval times. As mentioned before the bow of a boat usually comes to a point and in order to achieve this shape, shipbuilders needed to bend or bow the planks of wood.

Stern

The back of a boat is called the stern. This part of a vessel can vary in shape but in any modern power-driven vessel, the stern is usually flat at the back and doesn’t come to a point. The stern of a boat is also where a vessel will fly its national ensign to show what country the vessel is registered in.

The term stern was most likely brought to English from the old Norse word “styra”, meaning steer, and most likely became associated with the back of a vessel because up until power-driven vessels became the norm, ships have almost always been steered from the back.

Starboard

The right side of a boat is a vessel’s starboard side. While the two sides of the boat are quite similar, it is important to be able to distinguish between the two for the purpose of maintaining clear communication on board.

The starboard side most likely go its name for a similar reason as the stern. Essentially, before boats used rudders they were steered with steering oars from the stern of a vessel. Because most people are right-handed, this steering oar was usually placed on the right side of the stern. Eventually, the old English words “stéor” and “bord”, meaning steer and boat side, came together to make starboard.

Port

The left side of a boat is a vessel’s port side. Not surprisingly, the term port side also came from the way early boars were steered.

As I mentioned before, before rudders, boats were steered using large steering oars that were usually attached to the right side of the stern. With the steering oar on the right side of the vessel, it was much for a vessel to dock at the port and move cargo from the left side of the vessel.

This practice eventually manifested itself in the term larboard, meaning loading side, however, being that larboard is quite similar to starboard, it was eventually changed to port to avoid any unnecessary miscommunication.

What Do Red And Green Lights On A Boat Mean?

The red and green lights on any boat are called the side lights, or combination lights. These lights, along with all the other so-called navigation lights, help communicate your position to other vessels. By simply seeing these lights, other boaters can know exactly what way you are facing and whether or not you are moving toward them or away from them.

These lights are visible to other boaters if they are viewing you from either side or head-on, and they can help prevent collisions in situations with restricted visibility and help identify which boat is the give-way vessel and which vessel has the right of way.

The green light is located on a boat's starboard side, so if this navigation light is visible to another boater, they know that they are viewing your starboard side.

The red light is located on the boat’s port side, so again, if this navigation light is visible to another boater, they know that they are looking at your port side.

If another boater is able to see both the green light and the red light this signifies that they are looking at the bow of your boat and you could potentially be headed their way.

What Other Navigation Lights Do Boats Use?

Sidelights aren’t the only navigation lights that boats use to keep avoid collisions. In fact, the International Maritime Organization states that multiple different types of navigation lights must be displayed.

Stern Light

The stern light, as the name implies, the located at the stern of a boat. These stern lights are usually white and are only visible to other vessels if they are viewing your vessel from behind. Having a white stern light helps differentiate it from the red and green sidelights and makes it even easier to determine the position of a vessel.

Masthead Light

A masthead light is a white light located on the masthead of a ship. Masthead lights shine both forward and to the side allowing those steering the boat to see what is in front of them. All power-driven vessels above a certain length are required to have a masthead light lit while using engine power.

All-Round White Light

In the case of vessels under 39.4 feet in length, all-round lights can be used in the place of a masthead light. This all-round white light essentially combines the masthead light with the stern light and, as the name implies, is visible from all directions.

Towing Light

A towing light is a light only used in the case that the boat is a towing vessel. These yellow lights are located at the stern of the ship, usually right above the stern light. Even if the vessel is not specifically built for towing, if a commercial vessel is towing anything, the stern light may be replaced with a yellow towing light.

Towing lights are important as things like barges don’t often have their own lights to illuminate them, so the towing light is necessary to ensure that other ships are aware that the vessel is in fact towing something and that they should stay away from the back of the ship.