If you’re looking to get fit but jogging doesn’t appeal to you, and you find stuff in the pool other than swimmers turns you off, then you may want to look at cycling.
In the greater Tokyo area (Kanto Plain), riding isn’t always that great in Tokyo but there are some great places to go outside the huge metropolitan city. Some of the best places are along the rivers where the communities have actually maintained a cycling road that goes from Tokyo bay up stream.
For example, you can ride from Tokyo Bay up the Edo River and target Sekiyado Castle as your goal. The castle turned museum even has racks to hang your bike and picnic tables to each your lunch or relax on the borders of Chiba, Ibaraki, and Saitama prefectures. the cycling path varies from the size of a two lane road to a small paved path that only can handle a rider each way.
In the above picture you can see a sign in Kasukabe-Shi (City) Saitama along the route saying you’re 45 km from the ocean.