Pic from Wildgravity.
I believe this straight slide run out for the vertical drop slide is the piece that is shown to be underwater in the latest promo video. I am really curious to see how this plays out. Currently the water line does not look like it would get above the slide based on the surrounding walls. The white cover appears to be where the slide will be clear and go underwater. Will be interesting to see how/if a pool gets built around it. The wave pool to the right already looks pretty deep at that point.
I do find it a little odd that Universal is using the 'slide underwater' gimmick. I don't think it has really played out well in its other iterations (Aquatica / Atlantis). But maybe this will somehow be different.