Aquafit (shallow) 45:00 
2nd of 3 free visits to the Y. First time trying aquafit. Was supposed to be in deep water, but the floor wasn't cooperating, so shallow instead.
I may have been, shall we say, the participant with the least amount of gray hair. Not sure if it's because it was a weekday morning, or if that's the typical demographic.
Everyone can adapt the workout by choosing their own intensity. Still, didn't feel it was anywhere near as aerobic as running or spinning, but it was fun for a change of pace and hopefully provides other benefits.
Strengthening (machines -- various) 1:00:00 
Tried out the various weight machines. Fun to tack on before or after a class.