If you tube within the city limits of New Braunfels then you can only use coolers that are 16 quart in size or smaller.
If you tube outside the city limits, you can do whatever you want.
If you tube the Comal, you are in city limits. If you tube the Guadalupe from Gruene bridge and down (starting at Rockin' R for example) you are in the city limits. If you tube _above_ the Gruene Bridge and get out there, you are _outside_ city limits.
We tubed July 4 on the Guadalupe and went from the Gruene Bridge down. We did that b/c I was worried that above would be too low due to our droughts (it seems in the past to be more affected than below the bridge). We had 10 people and 4 16 quart coolers. We had 2 tubes for coolers -> each with 2 16 quart coolers.
The rule is idiotic -> it doesn't matter how many coolers you have, just the size of the coolers. Fortunately 2 of us had 16 quart coolers so we had to rent only 2.
Go 35 to 306 and find Abbots. $20 for a tube with a bottom and they usually charge just $10 for your beer cooler. Take the four hour float the the fourth overpass. They'll pick you up and drive you back. It's a huge bend. No cooler limit or other stupid laws other than no glass. Did it just two weeks ago, and the water level is just fine. Still some challenging rapids where you'll bust your *** if you're not ready. Have fun.