You can definitely swim in the pools below the falls. Don't think jumping off the surrounding rocks or falls would be a good idea. Heads up that you need to climb down and back up a very steep path to get to the swimming spot below the falls. Good shoes highly recommended.
There are some small ledges and a nice swimming hole above the falls a ways. There is a trail. I've jumped off the ledges with friends and kids. Good times. Just be aware of your surroundings. Be safe and have fun.
I haven't seen anyone survive a jump off the waterfall and do not know how deep it is below. I have seen some people swimming in the shallow upper portion with their dogs.
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