Seconding (thirding?) the freedive fins recommendation. I am horribly addicted to all mine and hand carry them whenever I fly (I can even strap them to my backpack skateboard style).
I'm currently trying to find a pair of regular shorter scuba fins for tech stuff (wrecks, caves, etc) because the freedive fins don't always work well for that but it's really hard finding something that has anywhere near the effortless power of the long fins.
I'm willing to trade some of that for precision and the ability to move in tight spaces, but damn it's hard to go back.
I'm currently trying to find a pair of regular shorter scuba fins for tech stuff (wrecks, caves, etc) because the freedive fins don't always work well for that but it's really hard finding something that has anywhere near the effortless power of the long fins.
I'm willing to trade some of that for precision and the ability to move in tight spaces, but damn it's hard to go back.