Their instruction manual says "The sensor can be inserted in a bulb well for immersion sensing".
According to that statement I would say they don't reccomend it.
I have had mine submerged in a bottle of water for about a year now without a problem, but if you want to be on the safe side make your own type of well. Place the sensor into something you can submerge into the bottle. Just make sure you use something that is a good conductor of heat and that the sensor makes good contact with its outside wall.