The brigs don't do it as often as spixies and marisas do. But they will bury themselves on occasion. I find my spixies buried in the gravel--I don't have sand, but gravel works just as well for burying yourself
--every day. I don't know if it's to protect themselves when they're sleeping because I've seen them sleeping on the glass too. My canas will look like they're burying themselved but they're actually excavating a particularly delicious tidbit under the gravel
. And the nerites can get to the glass at the bottom of the tank and eat their way along--leaving a ditch behind them! So I wouldn't worry about it, some snails just like the feeling of being buried and feel safer I guess. Snails--who can figure them out?