The water between Calcasieu Pass and Mobile does not behave like a coast. It behaves like a marsh with shipping channels cut through it. Open bay on the chart is often thin water with one dredged line down the middle, and that line is the part of it a boat with any draft can actually use. Mississippi Sound reads as open water at a small scale and is not, and the same holds for most of the bays west of it. What you want out of a chart here has less to do with how deep the water gets and more to do with where the bottom stops being soft and starts being something somebody put there.
The Alabama, Mississippi and Louisiana pack is built from 357 official NOAA ENC cells, the second-highest count of the 18 US regions. Inside it are 115,671 individual charted soundings, 20,780 charted depth areas and 20,042 depth contours, together with 9,771 charted obstructions, 2,447 wrecks and 1,967 dredged areas. NOAA publishes tide predictions for 137 stations inside the same box. The whole pack is a 44 MB download.
This region carries 6,003 charted lights, the highest count of any of the 18 US regions. The split underneath that number is the part worth knowing. There are 3,822 lateral beacons against 1,008 lateral buoys, close to four fixed marks for every floating one, and the beacons rank third in the country while the buoys rank eighth.
That ratio is the region in one figure. Running this water is pile to pile. A beacon standing on the bottom does not drag and does not go off station in a blow, which counts for something in a place where weather moves water around. It also stays exactly where it was after the channel beside it has shifted, which is the other half of the same fact. There are 15 safe-water marks in the entire region, so a mid-channel fairway mark is rarely what you are being handed. You take your position off the structures beside the cut.
| In the chart pack | Count |
|---|---|
| NOAA ENC cells | 357 |
| Charted soundings | 115,671 |
| Depth areas | 20,780 |
| Depth contours | 20,042 |
| Lateral buoys | 1,008 |
| Lateral beacons | 3,822 |
| Charted lights | 6,003 |
| Anchorage areas | 156 |
| Bridges | 1,292 |
| Overhead cables | 1,018 |
| Dredged areas | 1,967 |
| Charted wrecks | 2,447 |
| Charted obstructions | 9,771 |
| Underwater rocks | 57 |
| Restricted areas | 590 |
| NOAA tide prediction stations | 137 |
Counted from the Helm chart pack for Alabama-Mississippi-Louisiana, built from official NOAA electronic navigational charts. The pack downloads at about 44 MB.
The pack carries 57 charted underwater rocks, which ranks 17th of the 18 regions. Against that it carries 9,771 charted obstructions, the highest count in the country, and 2,447 charted wrecks, the second-highest. The danger symbols on this chart are wrecks and obstructions rather than natural rock, and that changes what a depth check is doing for you.
A bar or a ledge announces itself as shallow water, and a draft-aware plan catches it without being asked. Something standing on the bottom in water that is otherwise deep enough for your boat does not read as shallow at all. With 12,218 wrecks and obstructions charted across one pack, the hazard layer here is doing as much work as the sounding layer, and a leg that clears on depth still deserves a look at what it passes close to. Helm reports how near a route leg runs to charted hazards, and in this region that is a sentence you will read often.
The practical version is to zoom in before you run the line rather than after. At a scale where a whole bay fits the screen, a dozen obstruction symbols can sit underneath the width of the route itself. Keep a lookout as well, because a chart records what was surveyed and not what is floating in the cut this afternoon.
There are 1,967 charted dredged areas in this pack, more than in any other US region. Their charted depths run from 0.0 m up to 17.0 m, and the median sits at 6.2 m, a little over 20 feet. Half the dredged water in this region is charted at that depth or less.
The figure matters because of how loosely the word gets used locally. A cut through a marsh bay and a deep-draft ship channel carry the same symbol on the chart and the same word in conversation, and one of them is 17.0 m while the other is nowhere near it. The 6.2 m median is the honest middle. When you are working out whether a cut is worth taking on a falling tide, the number to read is the one on that cut rather than the category it belongs to.
Maintained channels also shoal between surveys, so Helm says which kind of number it is showing you instead of presenting a charted depth and a recent survey as the same thing. With 1,967 dredged areas in one region, that distinction comes up here more than almost anywhere.
Read the station list for this region and you notice what it is made of. It is mostly passes and bayou mouths rather than harbor entrances: Barataria Pass, Caminada Pass at the bridge, Chef Menteur Pass, Calcasieu Pass, Bayou Rigaud at Grand Isle, Catfish Point on the Mermentau River, Bon Secour on the Bon Secour River, Bayou La Batre in Mississippi Sound, and Biloxi at Cadet Point in Biloxi Bay. Chandeleur Light stands out on the islands. One of the 137 is a platform, COX WC-53.
The density is the useful thing. Water that gives you trouble in this region is water moving through a narrow place, and a prediction earns its keep when it comes from a station in the same narrow place rather than from somewhere a long way off with a different bottom in front of it. With 137 stations inside the box, the nearest one to wherever you are waiting is usually close enough to be about your water.
Four counts in this pack are worth knowing before you plan an inside passage.
Behind all of it sit 357 NOAA ENC cells, the second-highest count in the country. A coast cut into sounds, bays, passes and canals gets charted as many separate cells rather than a few long ones, which is why the cell count runs ahead of everything else in this pack, and all of it comes down as a single 44 MB download.
These counts describe what the chart pack carries, not the state of the water today. Charted data ages, channels shoal and marks move. Keep a lookout and verify locally.
Yes. This pack runs from 93.9 degrees west to 87.6 degrees west and from 28.8 degrees north to 30.8 degrees north, so Calcasieu Pass across to Mobile is one download. It is built from 357 official NOAA ENC cells and comes to 44 MB.
A draft setting handles water that is too thin for your boat. This region carries 9,771 charted obstructions, the highest count in the country, and 2,447 wrecks, against only 57 underwater rocks, so much of what is charted here stands on a bottom that is otherwise deep enough for you. Helm reports the shallowest point on a route and also how close the legs run to charted hazards.
Bayou Rigaud, Grand Isle is one of the 137 NOAA prediction stations inside this pack, and Barataria Pass and Caminada Pass at the bridge are on the same list. Helm reads the station nearest your position and labels the figure with where it came from.
Helm Boating