Well, the water shouldn't flow inside unless you put a block under it that would redirect the water to flow around it. I would still suggest a wall so you dont get sucked in, though you should be able to swim up and out in time.
Wait... In your title you said "3.1.3" but in your post is was "1.3.1". Might want to fix that... I'll get to work on examing the code and such.
Edit: Ah. Its having errors with Windows 8, from what I can see. Also try updating Java if you can...
*Morgan Freeman (from Batman Begins) voice* Oh, you wouldn't be interested in that. *end* We have those. It's called 'HELEN KELLER' and comes with a new avatar.