I got this image shortly after portal was released. I think it sums up the eating yourself idea pretty well:
http://img503.imageshack.us/img503/8612/portalllxf0.png
As far as the portal under the ocean concept, I'm actually hoping for dynamic fluid portalability being in the next incarnation of portal. Whenvever that is.
As for how high the chute of water would be, if the portal A was above sea level, and portal B was at the bottom of the ocean... Well, that would depend on how far down the bottom of the ocean is where the portal B is.
If it's 500 meters down, i'd think the gyser of water coming out portal A, would be equal or a little less than to the depth of portal A.
Of course, then we have to make the assumption that if you place a portal underwater, that the water would go through the portal at all.
I only say this, because i'm a geek, and watch a lot of stargate.
Not that it's nessesarily a way of proving or disproving anything, Stargate SG-1, Season 4, episode 7 (Watergate) shows them going to a world where the gate is underwater. They explain that when a constant pressure is being exerted at the event horrizon, that it would ignore that. That way, it prevents an atmosphere from leaking into space, or a world being flooded.
I would think the Apature scientists would also come to this conclusion. However, as I mentioned this isn't stargate. The rules may or may not be the same.

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