Day trip Onsen/Beaches from Japan

I will have a jr pass and travel of 2-3 hours on a train doesnt bother me. What would be the best onsen and beach to go to if im staying in Tokyo?

Onsen - Hakone or Yugawara has great onsens. Yugawara is basically an onsen town with cheap rates

Beaches - Izu and Shonan are awesome beaches, August is a good time to go since it'll be after raining season and the crowds will be out having a good time. Enoshima is a great place too.

A day trip to an onsen always sounds bad to me, because I think that onsen are best enjoyed as part of an overnight stay.

If you have enough time and money for an overnight stay, I recommend Kusatsu for its outstanding waters:
http://www.japan-guide.com/e/e7400.html

If you prefer a day trip, I also recommend the Hakone area because it can be reached in under two hours.

A few more ideas:
http://www.japan-guide.com/e/e2292_where.html