How to Navigate the Intracoastal Waterway


The Atlantic Intracoastal Waterway is a shipping route in the United States that was completed on June 18, 1949, and runs for 3,000 miles along the coasts of the Atlantic and Gulf of Mexico. It begins at the Annisquam River in Massachusetts and heads south, following the Atlantic Seaboard and winding around Florida to end at Brownsville, Texas on the Gulf Coast.

The route is federally maintained and toll-free. It uses a number of rivers, canals, bays, lagoons and sounds, and serves ports all along the Atlantic. The Intracoastal Waterway has many connections to inland waterways along the route, much of which supports deep-draft vessels. The shallowest depth is at the Dismal Swamp Canal, located in Virginia and North Carolina and measures 6.1 feet.


Historically, the route was used during World War II to avoid submarines at the coast. There were originally plans to link New York City to Brownsville, Texas. However, there was never a canal completed through northern Florida. Instead, the route is comprised of two sections: one along the Atlantic coast and the other along the Gulf of Mexico.

The Meaning Behind the Name

It is referred to as the Intracoastal Waterway and not the Intercoastal Waterway for a reason. The term “intra” means within, while “inter” means between. Since the waterway runs along the Atlantic and Gulf of Mexico coasts instead of equally between two coasts, intracoastal is a better term.

Current Uses of the Intracoastal Waterway

Today, the Intracoastal Waterway is used by both commercial and recreational traffic. North of Norfolk, Virginia, the waterway functions primarily as a channel for barges and other commercial vessels. South of Norfolk, you’ll mostly find crafts using the waterway to travel south to resorts or enjoy the passage for a pleasurable sail.

The Gulf portion of the Intracoastal Waterway stretches for 1,100 miles between Apalachee Bay, Florida to Brownsville. The channel is 12 feet deep and 150 feet wide. Most of the waterway and the ports around Florida are used by recreational sailors. There is greater commercial activity around New Orleans and the routes east to Mobile Bay, Alabama and west to Texas. The Intracoastal Waterway connects to the Mississippi River from New Orleans and is a major shipping route for petroleum and oil field supplies.

Sailing on the Intracoastal Waterway

The Atlantic ICW is often busiest during the fall and spring months as snowbirds head down “The Ditch” to Florida for the winter before returning home once again. This section spans 1,088 miles from Norfolk, Virginia to Key West.

Sailors must motor instead of sail for the majority of the trip, but the ICW provides gorgeous scenery in return. Fortunately, there are parts of the passage where you can turn off the power and sail if that is your preferred method of water travel.


There are plenty of options to stop for the night or take shelter from unfavorable weather. Depending on the timing of your trip, you might find it difficult to locate an empty dock or free spot at a marina. Many of the smaller towns have docks you can stay at for free. After docking, you can explore the area. Or, follow the recommendations of your chosen ICW guidebook to find a good spot to pull off the channel and drop anchor for the night.

How to Navigate the Intracoastal Waterway

The Intracoastal Waterway is maintained by the United States Army Corps of Engineers for safety and a consistent depth. They aim to keep the channel at 9 feet most of the way, but fluctuations in the depth are to be expected. Changing currents and variations in the channel can form shallower spots where it is possible to run aground. It’s also entirely possible to transverse the entire route without any problems. The important thing is to watch for markers that indicate changes, know your craft, and proceed with care.

Navigating the ICW can be an enjoyable experience if you pay attention to your surroundings and follow your Intracoastal Waterway map. The markers are plentiful, giving you all the information you need to navigate the channel safely. Learn more about the tips and tricks for a pleasant and safe journey.

Waterway Traffic

You need to have ample experience in boating and sailing before taking on the passage of the Intracoastal Waterway. Some areas have heavy traffic, and you need to be constantly alert. There are typically a lot of powered boats, and some operators tend to pay more attention to the thrill of speed than their own safety and that of others on the waterway.

Keep a close eye on your surroundings at all times. Never let your craft get caught in tight quarters, especially close to multiple powerboats. The most populated areas tend to be located around the southern part of Florida. If you are in a sailboat, most faster boats are considerate and do their best to slow down when passing, but you should stay vigilant and hang back when necessary to let others go around you.

Understanding Aids to Navigation (ATONs)

The frequency of the Intracoastal Waterway’s intersection with other waterways and crossings can make it difficult to decipher the markers at times as the colored navigation aids switch sides.

Remember that ATONs run clockwise along the shore. Following the route down the Atlantic, around Florida, and along the Gulf Coast toward Texas is the ICW equivalent of returning from seaward. All aids are marked with a yellow reflective symbol along with their regular characteristics. During a southbound journey, yellow squares are port-side and yellow triangles are starboard-side.


The main ICW navigational aids are dayboards. These come in three forms:

  • Mounted on a piling
  • Mounted on a dolphin, or teepee-like piling
  • Mounted on a larger structure

The type of mounting doesn’t have any significance. All dayboards are clearly marked with large numbers. Red, triangular dayboards have even numbers and green, square dayboards have odd numbers. The numbers increase and decrease by one from one dayboard to the next. In an effort to keep numbers down to reasonable amounts, the ICW uses sequences of numbers that stop and start in a section, instead of a continuous count along the entire waterway.

If you encounter an aid that is lit, pay close attention. Most times, the light indicates a possible hazard or important turning point. The color of the light and the speed of its flashing give you additional cues as to its purpose. For example, a light that flashes quickly draws your attention to a turn involving an abrupt change in course.

Drop Aids

The Intracoastal Waterway is known to shift constantly. Sometimes, the Coast Guard uses drop aids, which are temporary markers, to offer more precise information regarding current conditions that aren’t reflected in the permanent markers. You can recognize drop aids by the letter added to the permanent marking designations. These temporary aids mark areas of concern, such as shoaling.

Mile Markers

Another navigational aid to guide your journey is the mile marker. Keep in mind that along the stretch of the Intracoastal Waterway from Norfolk to Brownsville, the markers show statute miles and not nautical miles. You can do your own conversions or use a table for a quick reference guide. Mile markers are small white signs with black numbers.


Overhead clearance for bridges on the ICW is 65 feet, with a few exceptions. Always watch the tide levels and proceed with caution as low-clearance bridges have been reported. The types of bridges you may encounter along the Intracoastal Waterway are:

  • Fixed bridges.
  • Lift bridges, which are typically found on railways and are usually left open unless needed for a train. When opened, they rise horizontally. Closures are marked with light and sound signals.
  • Single-bascule bridges, which have a single counterbalance with the weighted end falling and the unweighted end rising.
  • Double-bascule bridges, which lift in the center.
  • Single-pivot swings.
  • Double-pivot swings.

Swing bridges rotate or pivot open and require that you give ample room for the movement. All fixed bridges are at 65 feet aside from the Julia Tuttle Causeway Bridge in Miami at 56 feet, and the Wilkerson Highway Bridge in North Carolina at 64 feet. Some bridges have restricted hours that only open at scheduled times, and never on request.


Some parts of the Intracoastal Waterway have ranges marked with black dashed lines. These show shallow areas or those with cross currents. Range boards are rectangular and larger than other dayboards. The easiest tip to stay mid-channel is to keep the markers aligned and look ahead to the forward and rear markers.

Plan Your Intracoastal Waterway Passage

It’s important to invest in a good cruising guide publication to aid your travels. Familiarize yourself with the various navigation marks and adhere to the advice offered in your navigational guides. Stay informed about bridge opening times, be alert for boat traffic, and mind the depth and currents. Choose a guide that offers the most current information on the waterway along with details about the marinas and towns you will encounter. Check out our selection for some excellent material that is comprehensive and thorough. Our guides will be your indispensable companion for your entire transit of the Intracoastal Waterway.