Feel free to skip this entire post if you're one of the ones that feel there is "much ado about nothing" when it comes to the Nemo subs.
As you can see in the picture below, there's a new area that has been brightly painted with the new glass paint effects. The imagineers have even added in fake sea grass or seaweed, as part of the test.
I took this picture at maximum zoom, because it looked to me like they were also testing an animatronic figure, like a crab, but upon closer inspection, I'm not so sure. I think you're just looking at different colored rock here.