Fifty-Foot Falls was greatly enlarged by the flood of 2008 (open picture for more views). A small cascade hidden in the trees became a major drop, over 50' high. Because of its resemblance to the extinct Navajo Falls downstream, another unofficial title is New Navajo Falls. It's about 1/8 mile above the new Rock Falls. The flood not only enlarged this fall dramatically, it created two more notable waterfalls downstream (above Havasu Falls).
The pool is good for swimming, but too shallow for cliff jumping. Perhaps over time it will deepen. When it does, this will be a scary leap!
Notice how quickly the aprons form on the cliffs. Several large ones only 4 years old are visible. Algae grows on rock protrusions, which then become coated with travertine. Judging from the evidence here, it appears the large travertine aprons seen at Havasu and Mooney Falls could have formed relatively quickly.
For a tour of the canyon, see my complete Havasupai set.