There seem to be different flavors of flow.
There’s being thoroughly engrossed in a task to the point that self-consciousness of doing the task disappears. You are taken up by the activity, and only notice that you have been utterly engaged in it when you pop out, or “come up for air,” and realize it. Wow, we may feel, that was great – very fulfilling. And perhaps we plunge back in, and once again get so caught up in the activity that we aren’t aware of what we’re doing.
Another flavor of flow is when we do see ourself in action, and there’s a kind of blissful absence of agency. Although we are leaning the bike to and fro, avoiding obstacles with uncanny ease and speed, we don’t seem to have to engage the ordinary conscious response and reaction system. The movements, the shifts and dodges and weight adjustments are all happening as if by themselves. It’s a joy to behold, but even the joy has a kind of life of its own, and we have become a mute and rapt observer of all this well-being.
Samadhi likely has more to do with this second kind of flow. But in both cases the key ingredient making the experience happen so happily is the one that’s missing – me, the sense of self.