Swimming in Japanese rivers?

We've returned from Japan and one thing that struck me is that nobody seems to swim in the rivers over there even in 36C degree heat. Is it illegal or is it just because nobody does it?

I asked our taxi driver in Kyoto as we drove over the Kamogawa River in 35C heat if you can swim there
and judging from his reaction I'm quite sure it's 'forbidden'.
There were lots of people on a stinking hot Sunday gathered around the inviting river but none even putting their toes in!

It's not illegal to enter or play in Kamogawa (local rules may vary depending on the city).

You will find many people playing in the river on hot summer days. You also will sometimes see people fishing (wading in fly-fishing suits).

However, at least in Kyoto the condition of the river is very volatile. During the hottest periods when there's not much rain, the level of the water is very low in the locations where the river is easily accessible. It may only come up to knee height for an adult.
Conversely, in late August/early September the river can be extremely violent as rain water traveling all the way from Shiga Prefecture and beyond eventually flows into the river.

Japanese rivers tend to be small and may seem passive but there are deaths every year in Kyoto during the typhoon season.

Many rivers like Kamogawa have been engineered to ease the effects of heavy rains and reduce flooding in rural areas.

In addition to all that, Japanese people just are not as likely to wear trunks or a bathing suit in the middle of the city. The mentality is that swimming is for the beach or the pool and rivers are rather dirty places reserved for kids looking to explore "wildlife" and play with bugs.

And in truth, Kamogawa can get very dirty because, again, everything (including waste and trash from other cities) flows south through the city.

I don't know about Kamogawa, but at least in Greater Tokyo or Aichi Prefecture where I grew up, people have the impression that rivers in cities are filthy.

There are indeed people in Tamagawa enjoying fishing in a catch-and-release sense, but still you can easily go to a park where there are artificial streams designed for children to play safely or you can pay a few hundred yen to swim in your local public pool or school pool. If you go to the mountains, you see more people swimming in rivers near camping sites.

Out in the country we have river rafting trips, I went last year with my husband and his co-workers. We swam in and rafted down the Fujikawa river. It was fun!

Come to think of it I go quite often to Paris and London and have never seen people swimming in their respective rivers...mind you, with all the boats it would be dangerous..

Thanks for all the replies. In Melbourne, Australia there's no way I would swim here in the brown, filthy Yarra river passing through the city but in Japan most of the rivers we saw were crystal clear with abundent schools of fish life etc. even in the cities. (ie. Nagasaki, Hiroshima etc.)

A bunch of us Gaijin went with some Japanese friends to some waterfalls area in Mie prefecture and swimming was fine. Tourists took photos of us as we jumped off the cliffs into the river below. They looked envious of us since it was so hot. This group regularly goes to rivers on camping trips and goes swimming in them. I see no problem except that the Japanese are too shy to do this.

I see no problem except that the Japanese are too shy to do this.

I don't think they're shy but they're scared or causcious. As suggested, so many people die from jumping off high places into streams (which means that a certain percentage of them aren't scared or causcious enough).

On a related note, every time the Hanshin Tigers win, fans jump off the bridge into the Dotonbori River in Osaka, and a certain percentage of them have either died or gotten injured, not only because of the flow but because they get stuck in the mud.

swimming in japan is great experience because whole country is covered with water japan is like a island. so i like to read this kid of forum

I went swimming in rivers, creeks, lakes, ponds in Japan, USA, Australia & Argentina and I've survived so far.
Most of Japanese rivers are relatively short and cold & rapid upstream but as it flows midstream, there are many dams for hydroelectric power generation and farther down the water gets murky as sand which acted as the filter have been taken away for construction.
In Chikugo river in Kushu, when I was small we couldn't wait for the tide to go out so we could slide on an exposed mud dune. We didn't go when there were warnings after the seasonal rice pesticide was applied. The river became pretty dirty with trash, broken bottles & no sand. There have been many accidents and deaths from drowning and jumping off hitting submerged rocks. There are no laws but maybe warnings against swimming anywhere. Be aware even the water may look clean. It may be polluted from industrial chemical & house sewer dumping upstream.

Uco San, I think they die because of the nasty dirty water in Dotombori! :)