No, of course children don't always behave. But if a child is at risk of falling in lake, then I think a parent would have to be stupid not to be supervising them.
its not a case of stupidity, its the fact that it takes as little as 2 seconds if the child manages to get free of your grip and they are gone. it cant always be the parents fault.
I always worry with my son when we go past the lake, i keep him on reins or in a pushchair but some children dont have reins/pushchair. I would be very uncomfortable with him walking without a rein near the lake even if i was holding his hand.
I know this is worst case senario but think...
a hyper 3 year old whos just been told its time to go back to the hotel, he/she wants to stay in the park and is fighting all the way back to get their parent to turn around and take them back, they get free, spot the water, the reflections of the lights in the water ect and run for it. its cold and icy, the floor is slippy mum/dad goes after toddler but slips over and then within the space of about 5 seconds its to late.
If there had been a nice ornate fence around the lake by the dangerous parts when it opened and it was just part of it would you still see it as an eyesore? Fences and/or railings work as long as they are suited to the area... the fences around big thunder mountain, the area by POTC thats fenced off, loads of different places over there have fences and theres nothing wrong with them.