Not saying the woman didn’t die, but I’m finding it hard to believe that a healthy, conscious woman fell into knee-to-waist deep water, didn’t stand up to save herself, and drowned. There’s a photo in the link below which shows just how shallow British canals actually are. The water is knee-height, and two men are easily standing. In the middle of a canal, the water is waist-deep.
British canals also do not have currents and the water is still. I find it odd how they’re focusing on barriers (to stop people from falling into knee-to-waist deep water you can easily stand up in?) rather than the possibility of her being held down. The narrative just isn’t plausible at all. Any healthy, conscious adult, upon falling into waist-deep water at most, would simply stand up. If you ask me, something smells about this story (and all of the other "healthy, conscious adult fell into a shallow canal, didn’t stand up to save themselves with no explanation as to why not, and drowned" stories).
Them pointing out she couldn’t swim is a red herring. You don’t even need to swim in knee-to-waist depth water.
There’s no safety barriers because falling into a canal isn’t something that’s typically life-threatening to any healthy, conscious person. They don’t put safety barriers around paddling pools for the same reason.
When I was a teenager, I took a lifeguard training course at the local swimming pool. This was explained to us, as being far more common than you might imagine. Full grown adults can and do, drown in the shallow end of the kiddie pool, all the time. It happens so often, that they make a point of telling young lifeguards how often it happens, so they don’t overlook the shallow end of the kiddie pool, just because there are nothing but adults there at the moment.