The two notes below were actually submitted to the Cruisers’ Net in late March of 2012, in response to an earlier article about the Marco Island (Coon Key Pass) to Naples “waterway,” which appeared in January, 2012 (see /?p=25439). However, as there is good data here for Western Florida cruisers, we have put up a fresh posting here to increase visibility.
This “waterway” that runs from Coon Key Pass, behind Marco Island, and eventually north to Gordon Pass and Naples, is NOT a part of the official (maintained by the US Army Corps of Engineers) Western Florida ICW. HOWEVER, for vessels that draw 4 feet or less, this passage is an intriguing alternative to cruising between Marco and Naples.
There some real navigational quirks, and the depth limitation outlined above is based on one 4 1/2 foot spot, found near Goodland (southern Marco Island). Perhaps the trickiest section is an easy to miss marker, just south of the Goodland Bridge. If you miss that ATON, you’ll be giving Sea Tow some business every time.

We have run this inside route many times, but only once on a high tide, and that was really easy.
At below mid tide, skinny.
Also, don’t forget the markers change at the Marco Bridge, and the chanel takes a strange jog.
Capt. Sterling

I headed out in early on this route from Marco to Naples. I draw 4′ on my Hatteras and it was getting too skinny for me so I retraced my steps and went outside. The gulf was calm and we had a lovely cruise south. Turns out a large Searay which ran by me going full out found the bottom and ripped out his running gear. It likely a lovely passage, but very shallow.
John

Marco Island on Dwellable