My first wooden barrel!

This week I proudly welcomed into my home my first wooden barrel. Of course, humans have been making barrels for more than 2,000 years, but I find these oak barrels, still widely used for aging beverages such as wine and whiskey, to be a marvel of design and craftsmanship: curved wood, significant mobility given size, and watertight without caulking or glue!

I can think of several uses for an oak barrel including water catchment (rain barrel) and plant potter. However, I purchased this one, a ~60 gallon French oak cask made at Tonnellerie Rousseau in France and used locally by a friend to produce Pinot noir, because I hope to miraculously transform it into an ofuro (Japanese bath).  I'm not entirely certain at this point how that's going to happen, but I know I want warm/hot water, ideally solar-generated, and at least some circulation, while absolutely minimizing new holes in barrel, ideally utilizing only existing bunghole. I also need convenient, well-designed ingress and egress. Please feel free to comment as I am open to any and all ideas.