There are a number of waterfalls on Big Island.
Akaka Falls State Park has a short trail (about half a mile) leading to two tall waterfalls. Although the park is small, the whole area fills with lush tropical green trees.
Rainbow Falls in Waiuku River State Park nice, but the park is really just an overlook.
It rained, very heavy at times on my way to the parks. But luckily, there were short windows of clearing when I was in the park. Very happy I was able to take some pictures.
PS. It takes $5 to park at Akaka Falls State Park. However, if you park outside of the park, which takes few steps to walk, it only costs $1. I wish someone told me that. 🙂