Detroit and St. Claire Rivers
I used to keep my boat on Lake Erie and have done this trip dozens of times. Carib is right, the area is well marked. The only area of potential confusion is south of Fighting Island where the river opens wide.
The best way to avoid the larger traffic is to stay just out of the main channel in the shallower water. Parts of the Detroit have two sets of markers, one for shipping and another for shallower draft.
If you approach Detroit River from Lake Erie, you will encounter the current well before you enter the river. I used to stay to the east of the river entrance then run west parallel to the southern shore of Ontario into the current.
An interesting (and possibly buggy) side trip is to sail east of Walpool Island in Lake St Claire into the Chanel E''Cart. The Channel is deeper than it is wide in some places. You can round Walpool back into the St Clair River or can sail all the way to the little town of Wallaceburg via the Sydenham River if you wish.
I''ve spent the night in Detroit but I was always uneasy about it. I preferred the Ontatio Marinas near Peche (peach) Island. My only other stop was in the Black River in Port Huron. Turn into the Black River when you see a RR bridge permanently angled high into the sky (you might check ahead to see if it''s still there). Pass through several bridges until you see a grassy park-like area on starboard where piers line the river.This will be the the public marina. Good showers, fairly priced, and fun places to eat and drink nearby.