I thought this was the most impressive waterfall we saw while in Hawaii this past summer. It's the closest we got to a large waterfall and it is one of the largest waterfalls we saw. It it located on the Hilo side of the Big Island and if you are drive from one side to the other it is not much of a detour. I forgot the exact highway numbers but I remember its location being on the rental car map. Check it out, no hiking required.