ToME: the Tales of Maj'Eyal

I have finished the first quest destroying the portal that nagas were coming in from, was teleported to crystal caves, then
went to the world-map to find three areas that were accessible, 2 caves and a town. the rest of the map is cut off by water, and trees. I don't want to start all over again because I don't know where to go. Can anyone explain how to walk on water or whatever I need to do?

There is a gap through the trees.