The same kind of light paths that create a rainbow in the sky can produce a rainbow in the spray and mist of a waterfall.

This is one of the easiest rainbows to view. When looking for a rainbow in the waterfall, position yourself with the sun directly behind you and the waterfalls in front of you. The sun need to be shining brightly without clouds blocking and there must be plenty of spray in the air around the falls.

If you do not see a rainbow, then move around to different locations keeping the sun to your back.