The marketing on Universal's website literally says, "from the center of the raft"
I must admit, when I first read the descriptions I thought that spraying water from the center of the raft was misinformation and was referring to the yellow saucer slide with geysers in the concept art. However, now that all the slides are complete and I have reread the crazy slide names and descriptions I am starting to rethink some things. The description of a raft that sprays water is for Honu ika Moana.
Honu ika Moana™
Just like the ancient Waturi people who rode the ocean waves on friendly sea turtles and whales, guests can enjoy these two twisting, turning, multi-person slides. Honu sweeps up two massive walls, while ika Moana sprays water on riders from the center of the raft.
Based on this description I believe it is referring to the Blue and Dark Green raft slides by Cabana Bay, not the yellow and light green slides by I-4. The I-4 slides appear to be Maku Puihi Round Raft Rides.
Maku Puihi Round Raft Rides™
This six-person rafting adventure isn’t for the faint of heart. Choose one of two lava-tube paths or try them both. Maku slides through a deep volcanic gorge before spinning wildly around bowl-like formations. Then, test your bravery on Puihi, where you'll feel the stomach-flipping thrill of a zero-gravity hang time before splashing your way to safety at the bottom.
So the discussion on the missing geyser effect does not appear to be the same as water spraying from the center of the raft like many of us thought. I do hope the geyser effect is there, that looks way cool in the concept art. With all that said, I am not 'counting' on it but I would not be the least bit surprised if water will actually somehow spray from the center of the raft on the dark green slide Ika Moana. That effect would make what appears to be an average slide into something special.
We will find out soon enough!