How might a watery planet lose all of its water? How might a watery planet gain new water? Well, there are many speculations as to how water arrives on a planet, such as a near miss from a comet glancing the atmosphere, or one hitting the atmosphere and the severe temperatures turns the ice-water to steam, and when it cools it becomes rain putting water on the planet. There are other theories as well, but that one stands to reason. Okay so let's talk about this for a second, shall we?
Obviously when humans travel to other planets and moons they will be looking for water, because this life form requires it. If we can find it we need to make it, or extract hydrogen and oxygen putting them together so we have water to drink. Now then let me ask you a question; What happens on a watery planet or moon with barely any atmosphere and low gravity when a geyser shoots off and the water easily reaches near escape velocity? Well it just turns out that other people have been asking similar questions and come up with some rather interesting theories, theories which actually do hold water.
There was an interesting article recently in Space Ref Online News Titled, "Tidal Forces Could Squeeze Out Planetary Water," posted on February 9, 2012 - discussing an article in Astrobiology Magazine. The article stated,
"Alien planets might experience tidal forces powerful enough to remove all their water, leaving behind hot, dry worlds like Venus, researchers said. These findings might significantly affect searches for habitable exoplanets. Although some planets might dwell in regions around their star friendly enough for life as we know it, they could actually be lifelessly dry worlds."
If there is a large moon, or a planet which is tugging on a moon - that could create seismic events and heat within the planet or moon, and that would push hot energy and out gases up through its surface. Any water on that surface could be shot quite a distance into space. Perhaps even enough to escape the gravity dwell and drift away.
Certainly a moon could lose its water that way. Regardless of how the water got there in the first place. A planet with quite a bit less gravity than Earth could have the same problem, or similar circumstances causing it. Indeed, I hope you will please consider all this and think on it, as the scientists and researchers in this matter just might have something there.