The Riverwalk is very nice, lots of shade and any type of restaurant you could think of. There are lots of nice old buildings to look at. Many of the restaurants have outdoor seating right on the river.
I got out early one morning and saw a boat with hydraulic arms with nets skimming the top of the river and another boat with a pressure washer cleaning the walls from the river up to the side walks. They also have a few fountains that help to circulate the water, all that helps keep down any stagnant water smell.
The boat driver we had on the vote tour was very interesting. He warned us all to use sunscreen, he said when he started this job he was a 6' 3" white white guy (see picture of boat driver). He also said he had relatives that fought at the Alamo. He said his Aunt and Uncle were there 3 weeks ago and got into a really big fight.
It's a nice area and in walking distance of the Alamo, so if you venture to San Antonio stay on the Riverwalk.