They are live bearing cone snails,(AKA trumpet snail, MTS etc etc ) and yes they usually spend day light hours hidden in, and rummaging thru the substrate,
One of their attributes is that their constant rummaging keeps the substrate loose , from compacting, and from going anaerobic.

although they are slow growers, they can reach about an inch
.

Once established in a tank they can be difficult to get rid of, if that is the desire.

Assassin snails work.
I found the most effective biological control was using the Madagascan snail eating cichlids of the genus Paretroplus.
They can crush young snails, but have can opener like teeth that extract even the large tough shelled adult snails.

Some of these fish get large, 15" so not recommended unless the tank is adequate.
I had a large one I would shuttle between 20 tanks, that could rid a tank inundated with snails, in about 24 hours..

They are considered invasive species in some places , so care should be taken not to release the i natural waters.