Not only is relaxing on the agenda while you're traveling at speeds topping 200 mph, but sightseeing while soaking isn't a problem, either. One car will feature an almost 8-foot-long tub next to the windows, so missing the passing views won't be a problem. If you'd rather ride the bullet train without getting wet, the special train will also offer a lounge car with a bar counter (sake bombs?), a car of standard seats, and three tatami-mat (traditional Japanese floor mats) passenger cars.
The foot bath train will run for 120 days or so every year, mainly on holidays and weekends; all seats require reservations, so make sure you plan in advance and look for the E3-series train when booking. Eventually, all Shinkansen trains will offer the baths to dip your dogs.
[Rendering: East Japan Railway]