I found this from a interview of a finswimming champion: "What kind of fins or monofins do you use? (Brand)
Now rocket, and immersion, and I’m very grateful the masters, who made it: Viktor Panev, Igor Soroka, Alex Lichenko"
Just a guess, but logically it might be this way:
Have they done a different monofin (Immersion) for finswimming immersion and 50 m apnea disciplines? And Rocket is mainly for surface finswimming? I have heard that finswimmers may want a different monofin for immersion and apnea, so that the blade bends more and from larger area.
If it is so, the next question is: Is Rocket or Immersion better for freediving?
DD, when you contact Viktor, Igor and Alex, it might be worth asking this potential Immersion/Rocket issue, too.
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Here you can see how really much and from large area monofins bend in finswimming immersion discipline:
I don't know what monofins these are, this is just an example. In finswimming immersion is done with an airbottle, but their apnea (50 m adults, 25 m juniors) is done without extra air. So finswimming apnea is something like very fast freediving with extremely strong kicks.
A good HQ video, World Game's apnea 50 m 2009. In lane 5 is
Igor Soroka. Ofcourse
he is the winner with his own monofin:
Unkraine (Igor Soroka etc.) won this World Games 4x100 m with Rockets, Respect!: