The Swan, the Pike, and the Crab

If harmony be wanting to your plans,
Vain are your efforts, yours, or any man’s;
They end in disappointment all alike.

I once observed a Swan, a Crab, a Pike,
Drawing a treasure; all their power, their will
Exerted, yet it stood unmoved and still.
’Tis not its weight, its weight was very little;
Three powers at work, it budges not a tittle:
The Swan would fain soar upwards in its pride,
The Crab draws back, the Pike to the water side.

Who of the three was wrong? and who was right?
It might be all--it might be none--it might!