Let the scenery drift past from a slow boat
On a slow sightseeing boat you simply sit, and the scenery moves for you: a canal town, a mountain river, cormorant fishing at night, or in winter a boat with a kotatsu, a low heated table with a quilt over your legs. Choose one by the season and your mood. Most rides take 20 minutes to an hour, so one fits easily into a relaxed day.
A boatman's pole moves the boat along the canals of Yanagawa, past willows and storehouses, on an hour-long ride downstream. In winter the boats carry a kotatsu heated with charcoal, so you ride with your legs warm under the quilt. The company has an English page and takes bookings online.
Look up at Kurashiki's white-walled merchant quarter from the water, as a boatman in a sedge hat poles the boat along the canal and back. The ride is about 20 minutes, so it fits between walks. Kurashiki is about 15 minutes by train from Okayama, a stop on the bullet train line from Osaka.
A covered boat glides along the clear Shimanto River and passes under chinka-bashi, low bridges with no railings, built so that floods can wash over them. You spend about an hour on the river. Book at least two days ahead; the pier is in rural Kochi on the island of Shikoku with no station nearby, so most visitors come by car.
A boat carries you about 12 km down the Mogami River through a mountain gorge in Yamagata, while the boatman sings the river's old boat song. From December to March the boats are heated and run as snow-viewing boats. The pier is about 10 minutes on foot from JR Furukuchi Station.
On summer nights, a roofed boat with tatami seating floats beside the fishing boats on the Nagara River, where trained cormorants dive for ayu, a small river fish, under baskets of burning pine. The master, called an usho, handles the birds on leashes from his boat, and you watch from close by. The season runs from May 11 to October 15 each year, and an English pamphlet is handed out on board.
A covered houseboat that leaves from near Hamamatsucho Station in central Tokyo and cruises the waterfront while you eat. The tempura is fried in sesame oil and brought to you one piece at a time. It is a slow way to see Tokyo from the water without leaving the city.