ya it is fine if snails are out of the water I have bubble snails, turbo snails, cerith snails and in another tank some sea slugs and all of them love to get out of the water. No it is not bad water quality it is just they don't know any better so they will look for food in creative places if there is not enough, or if they see another snail/ slug they may follow them to find food. In fact just a few days ago I had put rocks on top of the aquariums because I had accidentally stepped on a turbo and found others following that one, I will always remember that day. so, they are fine out of water just, watch your step.