Can you snorkel down the river along with fellow tubers? Or is snorkeling not allowed in the tubing area?

Yes you can I seen a few people snorkeling when I was tubing

We always bring our snorkeling gear! They have a flag you can rent cheap... we are on and off our tubes the whole trip!

I would say go to the website for the rainbow River State Park. Because I'm pretty sure they prefer you to have a flag if you're going to snorkel just so boats can see you.

I have snorkeled down that River with people on tubes it's very beautiful