Apnea Freediving fins are designed for efficiency in energy transfer for straight line swimming with minimal effort. Fin blades are longer and often more flexible compared to traditional snorkelling or scuba fins. The length improves the energy transfer from your legs to propulsion through the water. Many freediving fins have different hardness blades for different divers or environments. Hard blades will move you faster but use more energy whilst softer blades will use less energy but won't move you as fast. Hard bladed fins are made for stronger more athletic divers in open water while a medium stiffness blade will be better suited for a beginner to average diver.