What Vibration?

You read the water; look for the change of color and texture that indicate a bottom change, and watch the contours of the shoreline. What's happening on land continues under the water. If the shoreline points out expect a shoal. Most of all don't just head for your next buoy. Draw a line from one to the other and keep looking back to make sure you're not crossing it. Also remember that buoys are only guides. In many places you can run out of water dead center of the channel, especially around inlets, hence learning how to read the water. A big saving grace that the OP is familiar with is that most of the east coast below New England is a sand or mud bottom. It's fairly forgiving. When you grow up in places like the south shore of L.I. 3' depth is plenty. At 6' you start singing a happy song. Personally I find inland rivers much more challenging. Depending on drought levels you might find a 20' tree sitting below 22' of water.

Don't think I'd limit it to pod boats. Basically when in doubt follow someone bigger than you.

I have three suggestions having done this many times- run outside when the weather permits - go really slow inside when you are even in questionable areas or passing and this last trip down a few weeks ago I used Aqua Maps with the USACE survey overlayed. Also I used Bob423 tracks overlayed ontop of that to seal the deal. Bob has an extensive resume of running the ICW and he records his tracks for people to use. I have found them to be really excellent and reliable! http://bobicw.blogspot.com/p/bob423-long-tracks.html

I use my regular Garmin plotters for most things but when entering the inlets and on the ICW I use Aquamaps on a big iPad Pro in addition. I like the fact that its easy to update the charts and the USACE surveys update regularly. The surveys are incredibly useful. Just another tool....

Having run the N/S-S/N route over 100 times you're making too big a deal out of it. I've touched bottom twice in all those times. Once with the Hatteras (5' draft) by an inlet just north of Charleston where I saw it coming. Just put my bow into the sand and anchored till the tide came in an hour later. First time was mid-channel just north of Carolina Beach with a 3' draft. Again could see it was dicey but that bent a prop even though we were going dead slow. Worst thing about the ICW is that it's gotten so SLOW with all the development the past couple of decades. Get you updates on Salty , relax and enjoy the ride. But pay attention every minute. Due to it being so SLOW though outside is definitely the better and more relaxed place to travel. I am surprised that nobody has mentioned the Rock Pile up by Myrtle Beach. A little pucker power there with a big boat. Not real hard but there's no small misses there.

Good to hear you take good care. I wouldn't own a boat, and unfortunately have found you to be the exception rather than the rule with the boats I've run. Of course running the ICW requires homework and vigilance. You'll notice my admonition to "pay attention every minute". I always carried paper charts for the entire coast and my personal GPS with routes marked on both for any questionable areas along with a full set of cruising guides and Salty's ICW updates. I also grew up on the south shore bays of L.I. which are basically big sand bars interrupted with little pieces of channel. So I might not freak out by skinny water as someone used to places like the Chesapeake. Just saying that the ICW isn't to be avoided just cause there's some skinny spots. Barges with 7'-9' drafts travel it all the time as do fixed keel sailboats. So there's water there, but it does require eyes open all the time (especially near the inlets in the Carolinas). I always encouraged owners to come along on the trip cause I consider it a college education in boating. My main reason for avoiding the ICW is time. Seems everybody through the Carolinas has put in a dock hoping they can sue some boater throwing a wake, and we don't even want to think about So. Florida. But if the weather forces you to the inside it's not to be feared. Just pay attention 100% of the time. It also helps if you know how to read the water as well as the charts. Look for that change in color and especially the change in texture. That's a change in depth. If you're in the crinkle and it's deep stay out of the glass and visa/versa no matter what the chart or the buoys say. One thing very few people realize is when their charts were drawn, and the ICW changes many times each year as the storms come and go.

I tend to side with NYCAP. I have done 100's of ICW deliveries. I have a chartbook that is marked throughout the way, but knowing what to look for, looking at latest reports, and going. I haven't damaged any running gear yet and most all of the yachts I've run through there are 50' and above. It is sad that the ICW is as shallow as it is though. In 2003 I worked on a 97' that drew 9.5' and we used to travel the ICW exclusively and there were only 4 small areas where we had to be careful.

As Nycap and Capt J said, I've been running the ICW north and south for 30 years, on all kinds of boats including tugs. For the last 12 years it has been the portion from Beaufort/Morehead to Norfolk twice a year on a 130ft motor yacht drawing 7-1/2 ft. As long as you pay attention, learn how to read the water and get used to the fact that you're running close to the bottom there is no problem. Be cautious, yes. Be scared to do it, no. It's a beautiful portion of the coast, especially if you want to avoid going around Hatteras.