So what is the happiness of fish? "Swimming about so freely, following the openings wherever they take them."
It is true, of course, that this is what fish do as a matter of instinct; they probably do not choose this behavior over some other. But we can choose, and I suspect that Zhuangzi is recommending that we, in our expanded capabilities, choose to live somewhat similarly. "Free and easy meandering", one way to translate the title of the first chapter (Xioyaoyou), sounds very much like just this.
The freedom to meander (swim) where we like is not the ability to go anywhere, however, but to be happy (like) going where we can. We can go wherever we are taken, wherever the "openings" take us. This freedom is thus not the ability to change circumstances, but to be happy in whatever circumstances we find ourselves. It is the freedom to "follow along", the freedom that does not depend on circumstances but is able to make use of every and any circumstance. Thus, the non-dependent one "chariots upon" every eventuality. We choose an attitude, not a circumstance.
I say "choose", but of course there is a great deal of work necessary to make this a reality. Why so? Because we have evolved psychologically in such a way that, unlike the fish, we are not content with our experience. We wish for something else. Immortality would be nice. Ultimate groundedness and guarantees would be appreciated. But Zhuangzi would have us apply the Illumination of the Obvious to our human experience and use that to realize an authentic and affirming response to our actual reality. This way is not a flight from our experience, but into it. But there are many in-built obstacles in the way of our doing so.
"In-built obstacles"? Yes. So, perhaps the first great leap is to learn to chariot atop these. Certainly we would not wish to deny or negate them — that would be to fail to make use of, follow along with, every eventuality. The first step toward freedom is to affirm our bondage; there is a great deal of freedom in this alone. When we can laugh at ourselves, we are experiencing something of this freedom.
You can check out Scott's writings on Zhuangzi here.