My Olive Nerite Snail Eggs Hatched
 

That's right. I have at least 6 new ones. They're extremely tiny, otherwise, I'd include a picture. My water is within normal parameters--not even close to being brackish. I don't have any other snails but olive nerites in my tank either.

You sure they aren't limpets?

or ramshorns?

Sometimes they come in on plants, other times they are accidentally scooped from the sides of a tank while getting the invert you want.

They may have hatched for some reason but will die as well. Look at amano shrimp, they will hatch in freshwater and you can see the zoa's in the water, but they have to be moved to saltwater quickly after hatching or they won't make it.