On an extremely high tide, which happens in that region, you can get through the Great Thoroughfare with a 4'-6" draft, but you have to hit it just right. I ran that slice through the island many, many times in a 21-foot center console fishing boat and frequently churned mud on the east end of the cut while drawing just 18 inches. Many of the island's watermen get through at dead low tide, and I have followed them through, but their boats are modified vee bottomed and draw very little water. Captain Butch Tawes and Curtis Johns showed me the best route through the Thoroughfare, which often was marked with just a pole sticking out of the mud.
That same area used to be much deeper, especially when Alan Tyler's Crisfield Lady, the mail and school boat, made a daily run from Smith Island to Crisfield to take the kids to school, pick up the mail, take on a load of diesel fuel and get supplies for Alan's restaurant. When the old boat began running aground due to siltation of the Thoroughfare he had a 105-foot catamaran constructed that zipped over the skinnier water like a shot, and was later used for one of his Tangier Cruises boats running from both Crisfield and Point Lookout. I wrote a feature story on Alan many years ago, and it was published in the Washington Post and Baltimore Sunpapers. He was a true entrepreneur and loved life to the fullest. Not sure if he is still alive, though.
Now, I was able to get through the cut in Tangier Island last summer with no trouble at low tide, though I did drag bottom in a few spots and I only draw 4 feet. Spent the night at Jim Park's Marina, which is pretty shallow as well, and I had to nose the boat into the slip because there was not enough water for me to back in. Though I didn't get to see Jim that evening, one of the other guys onboard went to his home and paid the slip rent, and when Jim asked who was the captain, my friend said "Gary Diamond." Jim responded, "is that old bastard still alive?" Than laughed as he took the money. At one time, Jim was big in the commercial fishing business, but found it a lot easier to just be a marina and boat yard owner.
The channel has silted in on the North Channel and if you draw more than four feet it's a good idea to favor the south side where depths still range to 7 feet at low tide.
I forgot to mention, the locations on the bay's western shore where you can take refuge and anchor for the evening. Solomons Island is an easy in and out location with lots of sheltered places to hole up for the night. Been there lots of times and never had a problem even during the worst weather.
Another is Point Lookout State Park, in Lake Conoy. You will have to anchor relatively close to the launch ramp, and not block it's access, but it is doable and completely sheltered in bad weather. The entrance through the inlet is about 7 feet deep, and depths to 12 feet can be found just out from the launch ramp pier.