Bob423/Active Captain and the Magenta Line

Our cruise north thru the remaining stretch of Georgia’s coast and into South Carolina was a continuing lesson in being in tune with the tides and currents. Georgia’s river basins and estuaries are second in contributing flow to the Atlantic only after Chesapeake Bay! With it’s 6–10 daily tides, the silty soils that support the rich shrimp, crab and oyster habitats also see lots of movement and shoaling in the waterways.

On nautical charts the recommended course is marked and known as the "Magenta line". Unfortunately many times in these dynamic tidal areas both the bottom depths/shoaling and the Magenta line are not up to date. For cruisers and deep draft commercial vessels this creates much uncertainty when navigating. What might have been deep enough last month is no longer. Last fall’s Hurricane Matthew also “stirred” things up. Further as much of the recreational parts of the Intracoastal Waterway receive little or no maintenance (Georgia’s representative, Jack Kingston has actually supported reduced funding for these efforts)…………. Well you get the idea. Oh, and I’m not a very experienced navigator either!

Some of our most tenuous passages have come in this stretch of the Georgia/South Carolina coast. While the majority of the Intracoastal Waterway is made up of existing natural rivers, many canals/channels had to be constructed to connect them all to make the waterway continuous (where it’s not or where it’s become too shallow you have to “go outside” into the open ocean!). Coupled with the high tides, these canals, frequently named “cuts”, typically have a unique current flow because they connect otherwise non-connecting waterways.

In the past weeks we’ve gone thru:

• Hell Gate (MM602)

• Fields Cut (MM573)

• Ashepoo-Coosaw Cutoff (MM517)

These boats are all "stuck in the mud" on Jeykll Island until the next tide comes up.

Like “The Miserable Mile”, a stretch of the Gulf Intracoastal Waterway we traversed last year, sometimes because of shoaling you need to cross these stretches in higher tides to keep from grounding. The downside is that sometimes these higher tides also come with much higher currents that want to help you stray from the safe part of the channel. Hmmmm……”… and a hard place”, I think is the phrase that comes to mind.

Ahead we still have:

• Elliots Cut, and the notorious

• “Rockpile” (MM349-352)

We owe a lot to a navigation app called Active Captain. It’s a social media-based software that runs inside our navigation mapping software and it allows us boaters to call out areas of shoaling and navigation problems to each other. In planning our movements up the coast this has become an invaluable help in identifying places to watch out for or what minimum tide/current we need to make a safe passage.

This sailboat cut the corner too early and ended up going aground. If he's lucky the tide will lift him off in another 6 or so hours.

Of course like many social media sites, there are experts and “experts” and you have to figure out who/what to believe. That’s where Bob423 comes in. Although we’ve never met him, I can guarantee you that if I ever do, I’m going to buy this guy a few docktails!