Answer
Yes, illusionist David Blaine performed a public levitation in London in 2006, floating above the River Thames for 4 minutes and 39 seconds in front of a crowd of thousands. Blaine was secured to a platform and used a combination of wires and pulleys to maneuver his body upwards. The stunt was part of his "Drowned Alive" performance, in which he also spent 7 days submerged in a water-filled sphere.