Specific freediving fins are essential to achieving depth quickly. Fin designs are constantly changing but mono and long fins remain freediving standards. The most important thing to look for with a set of fins is fit and functionality. You want your fins to fit well and feel comfortable. You also want the correct fin for free diving.
Long bladed fins provide the thrust and propulsion necessary for free diving. They are light and sleek providing efficient and non-energy wasting power.
The fin blades are usually fairly rigid, but some manufacturers do provide different blades that range in rigidity depending upon the dive application.
Cost: $100 to $300