Beaches in Japan to swim in September

I am looking for several beaches in Japan where one can swim without fear of jellyfish. Also calm clear sea and good sand is key point. I tested beaches in Kujukuri and Kamakura. Now jellufish but dirty sand and some waves. Can somebody advise me a good place and beautifull hotel?

A related thread:
http://www.japan-guide.com/forum/quereadisplay.html?0+55188

Hi,

I'm from the link that Uji was kind enough to post. Kannonzaki also has a nice little hotel right in front of a pretty museum.
http://www.kannon-kqh.co.jp/

Also, if you don't mind travelling further, you might want to try islands like Hatsushima or even further to some of the "seven islands of Izu". Beaches with white sand such as the island of Niijima makes the sea look prettier as opposed to the clean but black-colored sand of Oshima.

Needless to say, it would be great if you could travel south to tropical Okinawa. Miyako Island is my favorite.