Abzu requires no effort to play. There are no core mechanics other than to swim through the levels, enjoy the scenery and make your own interpretation of the story. There are no puzzles as such, just push buttons to open doors etc.
Despite this, it is still a joy to play. I played it all in one sitting. And through the 2 hour journey I found myself mesmerized by the incredible beauty of the scenery and wildlife on show. You'll swim through ancient underwater ruins with hieroglyphics and come into contact with giant blue whales but the story is deliberately vague. It's left to the player to fantasise and interpret their own thoughts about what happened.
One thing that really stood out though is the games incredible soundtrack. It perfectly matched what was on screen.
All in all, this hasn't a patch on Journey. Which the art director previously worked on. But considering it's short length, is well worth your time.