It also looks like it could be a Nerite Snail. Regardless, I'm 99% certain that there are no predatory bad Snails with that shaped shell. I'm also 99% certain that all the Snails with that shape of a shell are mostly Herbivores.
Don't look at 99% as good gambling odds with me though, as I was 99% certain that JJ Abrams wasn't going to be directing the new Star Wars movie and that the Browns were going to the Super Bowl in 1995.