Tested they were in summer of 2014 in the Red Sea, with little swell and hardly flow.
I could easily descend vertically to almost 8m without feeling to have, I would lose the fins at any moment.
I snorkeled every day for 1.5-2 hours. There were no signs of numbness still aching bruises.
The kicking is always equally stable, the feet do not "bend" sideways.
The opening at the toe washed sand and cuts out or does not press into the toes. The material falls in general and particularly to the sensitive passages from softer.
It is also essential that an accidental fall at the on / off of the fins in the water is not possible. Obviously, this is prevented by integrated air chambers.
All in all very good fins, especially for a prospective price (about 32 EUR including shipping;. 08/2014)
I would order them again and can definitely hesitate to recommend it.