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Friday, Oct 19, 2018 | Home

The Inside Route

The Intracoastal Waterway (ICW) is an intricate web of bays, sounds, rivers, creeks and canals that allows commercial and recreational traffic to navigate safe inside waters. While the route runs approximately from Boston, Massachusetts, to Brownsville, Texas, it is not, in truth entirely connected. Instead, it is composed of both long stretches of inshore passages and sizeable stretches of less protected near-shore waters.
If we begin in Boston, the route passes through the Cape Cod Canal and then runs down Long Island Sound, into the East River at New York City and then south along the New Jersey shore. Shallow-draft vessels that have less than 35-feet of vertical clearance can go inside at Massaquan Inlet and stay inside nearly to Cape May at the mouth of Delaware Bay. But most passage-making vessels must stay offshore to Cape May.

The ICW then turns north up Delaware Bay, runs west through the Chesapeake & Delaware Canal and then turns south down the Chesapeake Bay as far as Norfolk.

There the most famous and heavily traveled section of the ICW begins at Mile 0 and continues entirely inside for more than a thousand miles to Miami. At Miami, the main branch of the ICW runs behind (to the west) the Keys to Key West. The second, deeper but less protected branch, known as Hawk Channel, runs just to the east of the Keys, also as far as Key West.

After Key West, boaters must stay offshore up the Gulf Coast of Florida, past the Florida Capes and Ten Thousand Islands, as far as Fort Myers. Here the Okeechobee Waterway, which connects Stuart (on the East Coast) with Fort Myers, joins the Gulf ICW. From there the route stays behind the long string of barrier islands that begin with Sanibel and end 150 miles later at Anclote Key near Tarpon Springs.

Boats must stay offshore from north of Anclote, around the Big Bend to St. Marks on Florida's panhandle. From there the route stays inside all the way around the Gulf Coast to its end in Brownsville.

How Not to Get Lost

The ICW is not a ramrod straight canal that you enter in Norfolk and exit in Miami Instead the route jumps from sound to river to canal to stream to land cut, etc., to form a complex route that will get you where you want to go. In particularly complex sections such as Georgia, the ICW heads off in all directions of the compass as it works its way south. So how do you know where to go? Two ways.

ICW's Identifying Markers

While there are no road signs to point out the route's twists and turns, there are signs of a type on all of the ICW's aids to navigation. Each marker carries a small yellow triangle or small yellow square indicating, first, that this marker is part of the ICW system, and, second, whether the marker should be considered as a red (triangle) or green (square) marker on that system.

This can get a little complicated in spots, so close attention is required. First let's look at how to keep the right color on the right side of your boat. By far the majority of markers along the ICW will follow this rule: "Red Right Returning to Texas." This means that you keep red markers on your right (starboard) all the way south as far as Key West, and then keep keeping them on your right all the way up and around the Gulf Coast as far as Brownsville, Texas, where the ICW ends. Easy.

Now let's get to the complication. While most of the route is marked by ICW markers alone, there are a number of sections that are used by vessels not following the ICW. For example, the Cape Fear River is a major route for commercial and recreational vessels that have nothing to do with ICW. The Cape Fear River also runs north from Cape Fear Inlet to Wilmington, N.C. That means that red will be on the right for northbound traffic. But the ICW enters the Cape Fear River on the north and follows it south nearly to its mouth before jogging west at Southport. So here ICW travelers will want to keep the river's green markers on their right. To indicate this, the Cape Fear River's green markers all have a small ICW yellow triangle on them to show that these should be treated as red markers for ICW travelers. Is that clear?

The catch with this method is that the little ICW triangles and squares are just that . . . little. This makes them often hard to see until it's too late. They also get hidden by osprey nests and worn away by weather. It's not a brilliant system.

The Famous Magenta Line

There is a better way, and it's called the magenta line.
As far as anyone can tell, the magenta line first appeared on charts in 1912, long before the ICW was complete. In the 1930s, when the route was largely completed as far as we have it today, the line was meant to indicate the best route south. Since then it has remained on all ICW-area charts, though no one has taken responsibility for keeping it up, and so it became increasingly inaccurate as channels shifted. After years of complaints, NOAA decided to begin removing the line whenever it updated a chart. But this left travelers with no way to follow the complex route. More complaints followed. So now NOAA is rethinking the line. You will find it on most charts and navigation apps.

The important thing to remember about the magenta line is that it shows where the route goes, not the deepest water . . . and not always which side to take the markers. Think of it as bread crumbs.

All of which brings up the No. 1 rule of navigating the ICW: Always follow the markers you see in the water, not the markers you see on your chart, or on your chartplotter, or even on your navigation app.