According to the closed captions, the lyrics with “oohs” are,
"So put your hands across the water,
Mushroom,
Monsoon,
Come soon! "
Repeated before and after the big pause.
I don’t know enough about him to understand if they mean anything, but they track with his mouth. You can put on captions yourself to check if that’s what you meant. I only played a couple of minutes from 15 to 17.