Actually its not quite the same here. That lake and river flow to the bay, just as the sea flows back into the bay, something to do with access to an alternate plane of existence I think. Where the water in that place actually comes from here. Its more magically than a physical hole, but this was the specific needs of the client. They know its not realistic, but it just fits their setting idea. Otherwise the island seems to fall under natural laws in all other ways.

GP