I saw Waters a couple of years ago doing his The Wall thing (my wife loves that album, I myself prefer the Wish You Were here/Animals era, The Wall is to me a Waters solo album with the other guys guesting) and I was surprised that he's quite a heavy-handed player. Not in a bad way, but he digs in hard when playing bass, no professional experience ease about it. My guess is also that he must prefer high action on his instruments. He "works" the bass.
He has anchoring authority in his playing though, but supple he ain't.
He used Rotosound flats in the '70s. On live recordings you hear a definite springy 'boing' in the notes he plays. High action, chopping right hand technique, it's surprising he doesn't have tendon issues at this stage.
I've tried those same Rotosounds and they are hard work. Quiet strings that don't sustain very long at all. It's all in the thump! Hard work to play on them.
