Free diving is best done relaxed. You want to be able to relax after expending energy and ultimately while as well. Typically while spear fishing, you do not want to "kick around for a couple of minutes" .. I would imagine pro free divers kick a total amount of two minutes, (maybe not even) the remainder of time being spent "drifting" in full relaxed state. So to answer your question Yes, constantly kicking around under 10m for 2 minutes while on one breath is difficult at best.
I was recommend the elliptical machine to mimic most the wave you kick while diving. You can check out one of my first threads about my thoughts as a beginner.
I would recommend you keep trying the walking thing (please be careful of objects around you incase of blackout. You will see in my thread that I also do a "dynamic squat apnea" hold, which I was also recommend and like.
I will also recommend that you "never swim alone".
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