Why does his shell look like this?

I just got this snail and one other last week and his shell looks messed up? Could it be from rough water conditions from the place I got him? My other mystery snail I got a while ago had something similar with his shell but seemed to have gone away. Any advice?

I just got this snail and one other last week and his shell looks messed up? Could it be from rough water conditions from the place I got him? My other mystery snail I got a while ago had something similar with his shell but seemed to have gone away. Any advice?