A felucca is an Arab form of sailing boat. If you can't spare the time to sail down the Nile from somewhere upriver, just take an hour or so to relax while sailing up and down in the downtown area. Cairo from the water is surprisingly quiet.
There are several small jetties along the river bank.
You should be able to get a felucca for an hour for 50LE. Sunset is a really great time to go.