Fin blade material shapes both durability and performance. Rubber blades are heavier but extremely durable, holding up to years of regular use. Lighter thermoplastic and dual-density blades, like the Frog Plus's techno polymer and silicone-based channeling material, flex efficiently and reduce leg fatigue while still standing up to regular diving. The Pro Star's reactive polypropylene blade takes a similar approach, prioritizing light weight and quick thrust over raw stiffness. Larger, stiffer blades generate more power per kick but demand more leg strength, while softer blades take less effort but need a faster kick cycle to match.

Several design elements affect how a fin performs underwater. Angled blades and side channels direct water more efficiently with each kick, while stabilizing flaps, like those on the Pro Star, keep the blade tracking straight instead of twisting side to side. Channeling designs, like the Frog Plus's dual-density blade, transfer energy on both the up and down kick for smoother, more efficient propulsion. A secure foot pocket also matters: a loose fit wastes energy with every kick, while a snug one, whether open-heel with a strap or full-foot, transfers more power directly into forward motion.