When I was a lot younger, I was involved in a youth naval program (Sea Cadets... somewhat like a beefed up military version of the boy scouts). I did a 2-week training instructed by SEALS, and during that time, they let us rummage through some of their leftovers. Among these items were fins. They are U.D.T. fins. I assume these may have been a 'standard issue' fin, but I could be wrong, or things may have changed... maybe that's why they let us have them?
At the time, I didn't dive or have a reason for fins, but I thought they were badass... especially to recieve from the SEALS. I grabbed a pair of XL's so I could grow into them and always them in life, rather than be rendered useless 2 years later. Needless to say, I still have them, they fit like a glove (or should I say, sock? haha!), and they are actually my primary fins! They're extremely sturdy and I get loads of propulsion with minimal effort. They're a bit heavy compared to other fins, but I have absolutely zero complaints about that. I also feel like I'm part ninja when I put these on... since they have been issued to me by SEALS (which is hands down the coolest and best thing about 'em)!! I really love them!
That said though, I'm looking into getting another set of fins I can wear with boots on, as I can only wear these with bare feet. I'll definately be getting a similiar fin, but maybe with a spring strap this time around (got my eye on the Hollis F1's).