Who does the sea of Japan belong to?

This sea has a total coastal length of 6,000 km of which 47 percent belongs to Russia, 36 percent to Japan and 16 percent to Korea. The sea offers a common space between four bordering countries: North Korea with 25 million inhabitants, South Korea 50 million, Japan 128 million and Russia 145 million

It shows a lot of percentage in Russia. Are there coastlines or shores where you can swim?

While Russia is a cold country, being close to the Arctic Circle, there are quite a few tropical and subtropical beaches to be found in the Southern half of the country. These beaches also offer exciting sports and activities such as kite flying, surfing, swimming, fishing and much more.