I don't know what "hybrid" fins are!!!

[Nemrod]

I would like to see video of the two backing up methods. I thought there was only the wide sweep method using the wide sidewall which seemed flawed to me because there are good fins that don't have a wide sidewall.
I have trouble backing up anyway because I never recovered full rotation or flexibility of my left leg after a full hip replacement.

Well to further ruin your day, I think I can manage a third way. It is not pretty, it is not efficient but it can work. I use the back of my calves. My knees are bent so my legs are near 45 degrees and ankles bent to keep my fins parallel to my body, I then flex my legs upwards at the knees quickly to about 90 degrees keeping my fins still parallel to my body or even rotated up some to use the back of the blade. If the hole I am down in has a big, mean, green moray in it and the cave is narrow side to side but has some vertical room and the moray has dis-invited me I gotta get out of there some way or another. I usually have my hands on my camera handles so that precludes the usual and popular arm flapping methods so that leaves my third method as being a good choice in the heat of the moment. Sometimes you just got to make something work, anything is better than nothing. And the back of the calves method does work.

A big, mean, green moray with ill intent :

 

[tarponchik]

With the flutter kick, every movement creates forward propulsion.

Only if you keep your legs straight. In reality, however, many (if not the majority) of divers do what resembles riding a bicycle movements, pushing themselves forward when straightening one leg but canceling this with the forward-moving knee of the other leg. They only move forward because fins have greater surfaces than knees.

 

[Nemrod]

Only if you keep your legs straight. In reality, however, many (if not the majority) of divers do what resembles riding a bicycle movements, pushing themselves forward when straightening one leg but canceling this with the forward-moving knee of the other leg. They only move forward because fins have greater surfaces than knees.

They need to raise their saddle .