Good beaches or outdoor swimming pools?

I am going to Japan with my grandmother in July, 5 days in Sapporo then five days in Tokyo. I was wondering if we could find any really good beaches or swimming pools around either of the cities. The last time we went to Japan we visited one beach near Tokyo and it was horrible. It was deserted and the water was murkey and the sand was dark grey sludge, and this was supposedley the most popular beach in Tokyo!Also, are there any public Onsen where you are allowed to wear smimming costumes? I think I heard of one in Hokkaido, but it was also unisex.

Near Tokyo the beaches on the pacific side of Chiba are ok. Not really great though. Many surfers. Check out Kujukuri or Oami

Alisa,

I must say I've never heard of any "popular" beaches in Tokyo, so I am sure that the "most popular" one went to was murkey.

Secondly, the sand in Greater Tokyo is naturally blackish, so even if you go to the truely nice and clear beaches in Sagami Bay, you still have to deal with dark grey sand and water that is not blue.

I wonder what you expect in a beach. You might have to go to the Izu Peninsula to fulfil your needs.

As for pools, the nicer hotels always have pools and they accept visitors. But the hotel pools can be expensive, so you might want to go to one of the many public pools. Again I wonder what you call a "really good" pool. The outdoor pool in Hotel New Otani, Tokyo is very popular and opens on July 16th.
http://www.newotani.co.jp/tokyo/fitness/

As for onsen, are you saying you're looking for one that you can bath in your swimming suit but is for women only? I'm not sure if that exists. It's usually "swim suit and unisex" or "naked and separate gender." You may want to go to one of the many private onsen around Sapporo.

You could go here:
http://www.yunessun.com/english/yunessun.html
It is not too expensive, and there is a direct train (Odakyu Limited Express) from Shinjuku JR Station that goes to Hakone Yumoto Station. (around 2000 yen, 1.5 hours). You can take a bus or taxi to the hot spring resort from there.
If you are set on beaches, I used to swim all the time when I lived in Yokohama, there are beaches all along the seaside line on the way to Hakkeijima Sea Paradise. There is sometimes alot of seaweed on the beach, but if you don't mind that, the beaches are great. Take the Keikyu line to Kanazawa Hakkei Station then switch to the seaside line that goes out over the water. The beaches are on that line (I think around 1 hour from Tokyo to Kanazawa Hakkei). There are beaches in Kamakura too, but I haven't swam there. The big Buddha (Daibutsu) and the temples are cool to see there too.
Have fun!

Shonan area in Kanagawa (Zushi, Fujisawa etc) has some good beaches. Popular in summer with people from Tokyo. The water isn't so blue but it's not sludgy and gross either!

Only an hour's train ride from Tokyo.

Why dont you take an overnight ferry from takeshiba to shikinejima?
That is the only place in Tokyo I know of with nice beaches.
Shonan area is nice but the sand is still black and the water is still murky.
Yunessun is disgusting...unless your grandmother wants to witness the horror and stench of people bathing in curry and wine and ramen... the smell of chemicals made me feel sick. Of course you can go to the "fake" onsen area of Yunessun which is free of curry sauce and screaming kids but the experience and architecture is all so artificial, there are much much nicer places to enjoy onsen.

The southern most tip of Izu has a small beach that is often times used as a setting in dramas when they shoot a scene that's supposed to be in Hawaii. It's not near as good, but as close as you can get without going to Okinawa.