If you're really concerned with water conservation, only turn the shower on when you need the water:

• Step in, turn the water on to rinse/wet your body
• Turn water off, apply shampoo
• Turn water on to rinse off shampoo
• Turn water off, apply conditioner
• Turn water on to rinse off conditioner
• You can probably wash your face without turning it off because that shit takes like a second
• Turn water off, apply soap to your body (including genitals and anus)
• Turn water on to rinse soap off
• Turn water off, exit shower

It's not at all relaxing, but it cleans your body and minimizes water usage.

Or, we could have built homes to conserve water in the first place by using grey water multiple times before using it to flush our toilets.