I didn’t even buy it as a sound mask, I bought it because it looked nice!
I find the low rumble/buzz of the tiny water pump and the sound of the water tinkling down each step is so soothing and masks my T to imperceptible levels.
There’s also a coloured LED in the bottom pool which acts as something to focus on.
Only downside is I wake up needing the toilet every time I fall asleep to it...