Two operators run water buses up and down Sumida-gawa (Sumida River). Tickets can be purchased subject to availability before departure at any pier.
Tokyo Cruise Roughly twice an hour between 10am and 6pm, connecting Asakusa with Hama-rikyū Onshi-teien (¥980, 35 minutes) and Odaiba Kaihin-kōen (¥1260, 70 minutes); the latter may require a transfer at Hinode Pier. Advanced bookings are possible, up to one month, online.
Tokyo Mizube Cruising Line Cheaper but less frequent trips from Asakusa to Hama-rikyū Onshi-teien (¥620, 40 minutes) and Odaiba Kaihin-kōen (¥1130, one hour) and back. The schedule is seasonal, with only a few boats daily in winter.