The biological optimum for fin propulsion — measured head-to-head against the industry's bestsellers. Every claim on this site is anchored in independent science and public record.
FoldingFins use a patented mechanism that folds the blade along its longitudinal axis — engineered for divers who travel.
This is the only design in its class that folds without weakening the propulsion surface. After more than ten years on the market, it remains uncopied. The engineering came out of six years of joint research with one of Poland's leading defence and marine technology institutions.
FoldingFins™ is a trademark of EXOTECH Sp. z o.o.
FoldingFins were developed jointly with the Akademia Marynarki Wojennej im. Bohaterów Westerplatte (Polish Naval Academy of Heroes of Westerplatte), Gdynia — under project BIODIVE FIN, 2017–2022.
EXOTECH's contribution was led by Mariusz Szymański — co-founder and co-inventor of the patented folding mechanism.
The collaboration combined EXOTECH's product engineering with the Naval Academy's testing infrastructure — a dedicated water tunnel, a humanoid swimmer's-leg manipulator, and a research team of three core staff plus eight habilitated experts across biomimetics, underwater robotics, materials science and mechanical engineering. Reached Technology Readiness Level 9 — the highest classification, meaning the design is fully proven through successful real-mission use.
The methodology, the apparatus and the FoldingFins themselves were all published in peer-reviewed journals between 2020 and 2022.
In the 2022 MDPI study, FoldingFins were tested side-by-side against the Aqualung Express Fin and the Scubapro Jet Fin — measured in a swimming pool with professional swimmers, using high-speed image processing.
The Strouhal number is a dimensionless quantity that captures the efficiency of fin-like propulsion. Biology suggests an optimal range of 0.2–0.4 (Taylor, Nudds & Thomas, Nature, 2003). Inside that range, propulsion is energetically efficient. Outside it, you waste effort.
| Swimmer | Fin | Velocity | Strouhal | Within optimum? |
|---|---|---|---|---|
| male | FoldingFins BW | 1.28 m/s | 0.20 | ✓ peak |
| female | FoldingFins BW | 1.18 m/s | 0.27 | ✓ |
| male | Aqualung Express | 1.38 m/s | 0.23 | ✓ |
| female | Aqualung Express | 1.23 m/s | 0.20 | ✓ peak |
| male | Scubapro Jet Fin | 1.31 m/s | 0.29 | ✓ |
| female | Scubapro Jet Fin | 1.29 m/s | 0.29 | ✓ |
Source: Piskur (2022) Table 1. Six FoldingFins test cases across three prototypes (BW, B, W) × two swimmers were measured — all within the biological optimum range. The full table is in the open-access paper linked above.
In short: same optimal propulsion physics as the two industry benchmarks — in a fin that folds along its longitudinal axis.
BIODIVE FIN is a matter of public record. The project was funded by the Polish National Centre for Research and Development (NCBiR) and co-financed by the European Regional Development Fund — and the closure was formally recognized by NCBiR on 15 April 2021.
Independent verification — these claims are not "trust us." They are verifiable in public records and on the parent company's mandatory POIR disclosure page:
Industry recognition for the engineering and the category.
FoldingFins® is built entirely from Hytrel® ECO B — a high-performance thermoplastic polyester elastomer engineered for demanding applications. No other dive fin on the market uses single-material construction at this level.
Why it matters:
Open access papers are linked above. For everything else — drop us a line.
info@foldingfins.com