Yakatabune Harbor in Tokyo - One of the most convenient and comprehensive "harbors" in Tokyo
It's right back of the big Shinagawa Station (Bullet Train station)
Firework, Cherry Blossom, just Lunch or Dinner, etc.... Yakatabune is very attractive play spot (?) nowadays.
Tokyo is, more than you may imagine, harbor city and water front city as well (like Manhattan) and Yakatabune harbor is conveniently located near Shinagawa (the first stop - 5 min. - of the bullet train from Tokyo station).
Yakatamune is fun, for leisure purpose alone, not packed like the commuter boat, but everyone have the table with "horigotatsu (you can put your feet into the 'hole' dug underneath)", and each one of you will be served the meal. Some of them are actually cooked on board, like Tempura.
You can also go up the roof and look around, feed the seagulls, and take pictures around. Very, very nice experience all around the season.
(see here for my experience at the cherry blossom season:
And, it's quite safe. They just go up and down the canal and river. Safety code is very strict, capacity limit is always observed.
Check the brochure photo on the right, and website. It should be very accommodating.