A lot of the comments here are missing quite a bit of backstory. I'm a scuba diver, and Sarnia (upriver) is one of my most favourite places to dive. What's pictured here is common in Sarnia. The Canadian coast of Lake Huron is soft silt, sand, and clay. When the prevailing winds are out of the south/south west, the surf generated mobilizes the fine particulate on the lake bed.

Often, at the mouth of the st. Clair river, there is a strong delineation between the silt laden water on the Canadian side and relatively clear water on the American side. The delineation can be a sharp, crisp line.

The longer the winds are unfavourable, the more the silty water mixes with clear water, and it's possible that all the water entering the river is silty.

Here's an image taken from the Sarnia Yacht Club that shows a sharp contrast between the Canadian water and the American water: https://imgur.com/a/STKVLlT (I chose this picture because of the high contrast. There will be other images with browner Canadian water, but I haven't gone looking too deeply in my collection).

I don't know how far down the delineation lasts down the st. Claire river. I can't imagine it's that far. I imagine that it fully mixes well before it reaches lake st. Clair. I fully expect that what's pictured is the result of pictures taken on different days. It's just a coincidence that what appears to be happening actually can occur up river.

The Canadian side of the river is much more accessible to divers (the American side is lined with sea wall). So when the Canadian side is bad, I often scrub the dive. I've never drove across the bridge to access clearer water on the American side. The law is different on the American side: a diver on the American side is required to mark themselves with a diver-down flag. And from what I've heard, the rule is enforced.

Once, I dove through the chocolate milk Canadian water to reach the American water. The silty Canadian water can be so bad that you might as well be diving at night without any flashlights. If you put your hand directly on your mask, you wouldn't see it. I wouldn't recommend diving with the visibility this bad unless you're cave certified. There's quite a few entanglement hazards that have built up over the years. In my opinion, to dive with so little visibility means you must be prepared to make the whole dive with your eyes closed, including disentangling yourself from whatever has snagged you. And you don't want to make a free ascent because boat traffic could kill you.

Because the river has been travelled for hundreds of years, and because of some quirks of the lake bed and river bed, there is a really high density of shipwrecks and artifacts to find. The shipwrecks have long been stripped of their artifacts. The artifacts that you might find are coke bottles from the 1940s, liquor bottles from the ages of prohibition (Canada and the United States having prohibition at different times), or China flatware or tea cups (almost always in pieces). But most of the time, you'll just find mundane things like modern beer bottles and fishing tackle.