What happens if it starts to rain, do you have to get out of the water?

You only need to get out of the water for lightning. You will also have to exit any of the slide lines.

Throughout my stay at the Volcano Bay, it rained, but we didn't have to get out of the water. There were no thunders.

Only if there is lightning

They are all correct. Only if it's lightning and that is standard for all parks with rides also.