Speaking as a fan of hydrotherapy, you should probably figure out a way to get your meditative time without using that much water. There will come a time where you have to pay for it.
Your bathtub probably holds 80 gallons. With you in it, it's probably 40 gallons. Your shower flows 2.5 gallons per minute; half an hour's worth of showering is like taking two baths, or 285 liters of water. An hour's worth of showering eclipses this entire graphic:
I say this as someone who takes up to three showers a day this time of year: for sure 1 after biking 16 miles to work in 100 degree heat, for sure another after biking 16 miles home in 80 degree heat, and if I have to do any bike maintenance before going to work, 1 before I leave. And I say this as a massive proponent of Russian spas who has an appointment in a sensory deprivation tank in three hours. But I also say this as a fellow traveler in a world that is running out of water.
I read The Hunt for Red October when I was in 6th grade or so. It exposed me to the concept of "Navy showers" - where you get wet, turn off the water, soap up, turn on the water and get out. I did that for years. And while I can definitely appreciate sitting there with the water blasting you in the back of the neck (and while I can say with no hesitation that without cold water blasting my head every day I'd have long since died of heat stroke), it's a sensation you can find elsewhere.
The joy of onsen