Yes, they are shot with polariser.
If you are going to buy one there is two choices: 1. Linear, 2. Circular
Go for circular and learn how to use it well, as you must rotate to find best effect of polarising.
You may need a softening/warming filter as polariser tend to cool/blue the view.
If you have enough money and want to have a good piece you can go for B+W. Othervise Kenko, Hoya, Tiffen can do the job. If you have only one lens (let's say 52 mm) you can buy an 52 mm screw-in filter. If you have more than one you will need adapter rings.
If you use polariser at all pics, it will have lack of warmth. Learn how to decide using polariser at a scene.
"where the traveller goes, nobody knows ! "