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Hard to tell w/o seeing the shell. I have a green star snail that is that size, but I doubt that is what it is...Probably a margarita snail like stated. They are usually coraline covered.
It's not a margarita snail because margaritas have round shells and this snail has a cone shaped snail. The only two other choices possible is Astraea and Cerith. It's most likely a Florida Cerith because he stated it as 2-3" big. Astraeas don't get that large.