WATER!!!!! Oceans have been added to the game around the edges of the islands. You can dig out the sand, and it will fill the hole up to a certain point, where it will then hit an invisible wall. SOE is working on implementing running water as well as the ability to use it as a building tool, swim in it, etc.

https://forums.station.sony.com/landmark/index.php?threads/update-notes-05-07-2014.36449/