Fishing for depth in the ICW

To the editor: It’s usually not very dramatic. One moment you’re blissfully motoring down the channel, and the next you’re peering over the stern wondering where all the water went.

The U.S. Coast Guard and the U.S. Army Corps of Engineers tell us the “project depth” for the Atlantic Intracoastal Waterway is 12 feet from Norfolk, Va., to Fort Pierce, Fla., then 10 feet from Fort Pierce to Miami. Officially, there is 7 feet of water on the Hawk Channel side of the Keys, and there’s supposed to be 9 feet from Fort Myers to the Anclote Keys on Florida’s southwest coast. From Carrabelle on the Florida panhandle to Mobile, Ala., the project calls for 12 feet again. These ideals are met a high percentage of the time, but there also are lots of high spots. And with numerous hurricanes, runoff from land, and infrequent dredging, the problem areas have been increasing in recent years.

Even with the latest charts, many stretches of waterway, particularly the narrow, canal-like portions, have no printed soundings. Those accustomed to sailing where safety margins are measured in fathoms will find themselves sweating as keels skim just above the bottom. Don’t trust any charted soundings along the ICW – even in side channels that appear to be well charted – take your own readings constantly, and proceed with caution.

The silver lining in this muddy cloud is that most ICW bottom is soft – really soft! You’ll notice this the first time you try to pull up an anchor – you’d better have a bucket, mop, hose and a change of clothes ready. That anchor will come up dripping with black gelatinous ooze that smells like rotten eggs. You’ll curse it as you slither around on the foredeck, but love it when your 10-ton ketch slides to a stop so gently you’ll wonder if you just dozed off and were dreaming you were moving.

And then you get hit with the bad news again. That pleasant stop means your keel has just dredged a long channel to nowhere.

By the way, if you do go aground, never jump over the side to push off without testing the consistency of the bottom first. You may find yourself up to your neck in the black stuff.

Most ICW groundings are the result of inattention to the chart, the course and the navigation aids. Probably the most popular grounding style is to slowly wander a bit too far toward the edge of the dredged channel. This typically takes place between two well-spaced daymarks, which tend to be placed on alternate sides of the channel. In other words, after you’ve passed a red marker, the next aid is likely to be a green one located on the opposite side of the waterway.

It is tempting to pass close to the navigation aids, assuming that this will put one in good water or close to it. There are two fallacies to this approach. First, ICW aids often are right on the shoals or other obstructions, not between the channel and the hazard. Pass too close and you’ll be making mud pies for a few hours.

Second, if you successfully pass near one aid, you are in all likelihood very close to the edge of the channel on that side. A few moments of searching for the right chart or picking up your sandwich, and you’re aground.

There are two theories to staying in the channel. Some boaters believe in a reverse sobriety test: weave from one side of the channel to the other, always heading toward the next mark, no matter which side of the channel it’s on. The beauty of this dance is that you always have something to aim for and you are likely to know which way deep water is if you do go aground. The disadvantage is that you go aground more often as you are frequently skimming close to the shallows and hazards the daymarks are telling you to avoid.

I’m a firm believer in being a road hog – when there’s nobody else around. There are no double-yellow traffic lines on the water, and there is no reason not to drive right down the middle whenever you can. Split the difference between both sides, and you are more likely to be in or near deep water.

Dredges concentrate on the middle of the channel, and they frequently give aids to navigation a wide berth – transforming them into aids to grounding. Notice where the tugboats and barges go – right down the middle. If you’re forced out of the middle by one of the big guys, it probably means you’re being pushed into a shallower area.

You may wonder how it is possible to stay in the middle without something obvious to aim at. The magenta line shown on the charts is not really there, despite what some people claim.

Quite a few years ago, I was on a big no-holds-barred steel ketch outfitted to go anywhere. I was intrigued to see a relatively inexpensive fish finder mounted so the helmsman could easily see it. Drawing 7 feet of water, the captain wanted to be sure he always knew which direction to head for deep water. The fish finder provided a visual reference of how the depths were trending, in addition to the numerical figures.

With the finder, one can judge instantly whether or not the bottom is rising or falling off, and you quickly develop the habit of tweaking the helm a bit to see what the trend is to either side of your course – you’re not only reading the immediate depth, but you know which way to turn if the water starts to get too thin.

For purely capitalistic reasons, the huge market for fish finders has driven prices far below those of typical sailboat instruments, despite the increase in features and functionality. As far as I can tell, many of the sending units, or transducers, are exactly the same, so there is nothing to fear. I’ve also found that fish finders are durable, waterproof and sip electrical power. I’ve been using the same one for more than 10 years, and I think it’s the only instrument that is always on and has never failed, despite being mounted in the cockpit.

Strangely enough, I’ve even found them good for finding fish! My unit allows me to turn on little fish symbols that look like they’re swimming across the screen – my kids watch the screen like a Game Boy. When we see those little invaders, it’s time to zap ’em for dinner.

John J. Kettlewell is the co-author of the Intracoastal Waterway Chartbook: Norfolk to Miami and the Intracoastal Waterway Chartbook: Miami to Mobile.

Categories: Navigation