spirit of shabbos

Question

There was a discussion that took place in the forum a few weeks ago, and you said that swimming would be in the spirit of shabbos but watching TV or movies was not. Can you please define or give specific criteria of how to dtermine whether something is or is not in the spirit of shabbos. (bviously its not just my feelings on the issue because intuitively i would think swimming is not in the spirit, but you maintained not only is it ok, it's even fulfilling oneg shabbos)Thank you.