• The Comal River in New Braunfels is one of the shortest navigable waterways in the United States. The water temperature is a steady 70-72 degrees year round, which makes it refreshing in the Texas summer heat and warm enough for a morning swim in the winter months. One of the most popular things to do on the Comal River in New Braunfels is tubing it! It's pretty simple actually, just grab your swimsuit and head to the nearest River Outfitter.