Here are some links to fins that might be comfortable, all with a heel strap, NOT the traditional shoe-style.
DaFins, haven’t swum with them yet, but these’ll be my next pair…
I’ve used the Voit Duck Feet for 35 years (3 separate pair), and they start stiff, but loosen up over the years. I’d recommend ’em. I have a long and short blade pair, short blades are more flexible.
The Churchill fins are classic, I’ve got an old pair now that are at least 25 years old and super flexible.
Lastly, these are really light and comfy: Zura fins
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Here are the last three workouts, written:
Asheville Masters Swimming 