I spotted this sci-fi-looking fin at the DEMA show. As can be seen in the photo, the fin can be folded so that it does not take up much space in one’s luggage.
The foot pocket also fits all shoe sizes, since the size of the pocket can be adjusted or tightened, using straps that are inserted into the sole where they are attached with clips—this is nicely illustrated on the Polish manufacturer’s website.
The thin fin blade is made of a flexible material, which appears to be carbon fibre. The manufacturer describes it as an “innovative bio-mimetic membrane” designed like a fish’s tail. My immediate impression when I held it in my hands was that the fin was solid and well-designed. It did not seem like just another fancy idea but was a proper new design for fins.