Tubs really need to be larger so people can lay in them. Even then, it still takes about 15 gallons of hot water to submerge someone. If I ever get even marginally richer, it'll be one of the first things I do. A properly sized tub you can lay down in. Making your knees hurt from having to stay bent or having your entire torso stick out of the water sucks.

People shit on Shower bath shower, but Faye had the first 2/3s right. Get the quick gross shit off, plug the drain. Let it fill while you shower then fill the rest if need be. The water will stay hot longer and you can actually lay back and relax.

Edit: The main thing is people feel like they use less water when they shower. But it does nothing when you stay in that long. Seeing a tub full of water is way more visceral. I just invite people to plug the tub next time you start showering and see how much you actually use up in those 30 minutes.

Most low flow shower heads are 2.5 gallons per minute. It'll only take about 15 minutes to fill your tub enough to submerge yourself.

Meanwhile women also like their showers at roughly the temperature of the surface of the sun to scrub away all that self imagined sin and yuck so it's like 3:1 gallons hot to cold vs 2:1 for normal people.