Personally, I'm not a big fan of natural attractions that have been altered or created by people. However, the folks swimming at the base of the falls were having fun diving and seeking relief from the heat. So it could be your cup of tea.

During research for the now-defunct Hawaii Waterfalls book project, I learned that the Waihe'e Valley Trail was now closed off to public access by Wailuku Agibusiness (now Wailuku Water Company). In order to do this excursion these days, you need to book with Maui Eco Adventures (who have the necessary permissions to conduct tours here).

Go north on Hwy 330 (it becomes Hwy 340 after 2 miles) for 6 miles. Turn left (west) from Hwy 340 onto Waihe'e Valley Road (the turn from Hwy 340 is north of the 4-mile post; and immediately south of the Waihe'e River Bridge and the 5-mile post).