Fins
To practice this sport you will need fins. But there are a lot of different kinds of fins.
Moreover, the fins you need, will also depend on you !! For instance if you want to swim fast , you’ll need rigid ones but you will be exhausted. On the contrary, if your choice, is to take flexible fins, it will be easier to swim and turn up and down, but you will lose some quickness.
Here you can see a rigide one : 
