#1 most obvious "new product worth developing" in my mind. The DIR diver wants a fin that maximizes the efficiency of the 4 main kicks DIR employs: Frog, modified Frog, Flutter & Back kick.
Surely, in the nearly 40 years since the Jet Fin was first designed, it should be possible to design a better, more comfortable fin. Such a fin should also be built with spring heels, not straps. Clearly there's a definable market for such a fin - much more definable than "another fin for tropical divers who can't tell one fin from the next".
I suspect that if such a fin were developed, if it actually was demonstrably better, that it would generate substantial sales. Many jet fin owners haven't bought a "new" fin in years, and are unlikely to do so any time soon given the ability to get jet fins on eBay and through local connections. The size of the DIR market (or of divers who want DIR capabilities in their fins) is much larger than the commercial sales rates would suggest.
