Cycle across the sea from island to island
The Shimanami Kaido links six islands of the Seto Inland Sea by bridges, about 70 km from Onomichi to Imabari, with a cycle path the whole way. Rent a bike and ride as far as suits you, resting by the sea, and drop it off at another official rental terminal if you like. Check the wind, the sunset and the terminals' closing times before you set off.
The rental terminal on the Imabari side, at the foot of the Kurushima-Kaikyo Bridge, with rooms if you want to stay the night. A ride across the strait to Oshima and back makes a good short first course.
Three suspension bridges in a row, 4,105 m long in all, linking Imabari and Oshima. The bike path runs in its own lane high above a strait where the tide races at up to 10 knots and whirlpools form, with ships passing below.
A roadside rest stop on Oshima facing the strait, where you buy seafood and grill it yourself over a small charcoal brazier called a shichirin. It is also a rental terminal, so it makes a good turning point after crossing the bridge.