For me, I have always assumed that the drowning risk is related to a child falling in a pond. They can't fall in a Belfast sink. Especially if it is up on blicks as they often are style wise.
I do fnid the hysteria around ponds interesting though, so I might not be the best person to ask!
Dh is Dutch. In The Netherlands there is open, steep sided water EVERYWHERE. I mean in front of every building, in every street, in the park next to the swings, just sections of open water. (I am not talking about canals, just like ponds, but everywhere.
None of them are netted.
None of them are fenced
They are all steep sided with no entry or exit points.
Children don't drown in them.
When we moved to UK, our garden had a lovely pond with a wooden frame and grid over it. (The previous owner was a child minder) Dh was desperate to remove the wooden grid. I insisted he didn't. Our kids were 3, 6, 8.
He did some research, and found that the statistics are ridiculously low, something like 1 child under 5 in the last 5 years have drowned in garden ponds. Most cases of drowning are not in 'normal' ponds. eg a veyr sad case of twins drowning in a Koi pond. Koi ponds are deep and straight sided, so if a toddler falls in, the water is over their head, no foot holds and no way to get out. The other cases were huge ponds, more like lakes, which obviously are dangerous.
So, when our youngest was 5, the grid came off the pond.