Flood water is not crystal clear.

My comments were based on 30+ years of firefighting experience. It's interesting to see imagination at work and I didn't mean to disparage the content. My training tells me to plan for the worst, but hope for the best. Plus, I got a chuckle over dozens of parachutists landing on top of the firefighters responding to take care of their fire!

The elevator would take too long to deploy, not to mention other problems. The parachutist would need to have a place to jump from (usually, roof accesses are locked, and windows are sealed because of energy efficiency). Landing areas around most buildings are not in park-like settings as shown on the link. As far as the harness goes, I just shudder to think of untrained occupants trying to climb down the outside of a high-rise. The best way to save lives in a high-rise is to educate the occupants on what their role is when the fire alarms sound.