I've enjoyed escargot in Paris. That's good eating. But it's mostly herbed butter with a little bit of snail in it. Those snails are captive cultured and fed for the purpose of human consumption.
If you've eaten many pond fish, you know they often taste the way pond water smells. Fish meat takes up the qualities of the water the fish lives in.
I can't say for sure, but I'd have to imagine pond snails to taste pretty badly of pond water.