Have always wanted to take a trip on one of the boats that cruise along the rivers of Tokyo - especially the Himiko which has to be one of the coolest looking boats I've clapped my mince pies on - possibly the closest one will get to taking a ride on a space cruiser.
The boat has been around for a while now since March 2004. Have seen it a few times cruising down Sumida River and finally got to take a trip on it yesterday.
You need not make reservations - just show up at the pier and buy tickets. Not many people get on at Toyosu but a load of people get on at Asakusa and I imagine many get on at Odaiba too. I recommend getting on at Toyosu for a stress free trip unless you like waiting in queues.
The trip from Toyosu to Asakusa takes about 40 mins and costs 1060 yen for a one way trip.
This page at the official site shows the various lines that the cruise company serves. Himiko only serves a few and its not clear which lines so I recommend just giving them a call to find out the latest times and prices.
The Himiko travels along Sumida River which cuts through Tokyo heading North away from Tokyo Bay. Speaking of Tokyo Bay, one of the first sentences a Japanese friend taught me was "Tokyo Wan ni Shizumeru zo" or "I shall down you in Tokyo Bay." Have not had the opportunity to use that term until today - about 15 years after he taught it to me ^^;
The cruise will take you through many residential areas of Tokyo - a very peaceful area of Tokyo. If you have the time, you could consider taking the boat up to Asakusa and then maybe walking back down the river side down to Kachidoki where you can eat some Monja Yaki at Tsukishima. The Sumida River post has some photos taken from the river banks.
The tower under construction is the Tokyo Sky Tree. Its due for completion next year and will be the tallest building in the world. Its main purpose is to be of a certain height which can then broadcast digital TV across Japan. The other purpose is to allow Gundams to refill and reload ammo mid flight.