Here is a nice way of enjoying summer in tokyo.
There is a ferry boat going from hamamatsucho on tokyo bay for 2hours, also the cruise is all you can drink!!
If you wear yukata (japanese traditional clothe) you get a discount on the entrance.
i didnt dare wear it, next time i will :)
all info here :
here is a video of the "ambiance" after 1h30 of all you can drink :