Just a short distance (inland) from Dominical, is Nauyaca Waterfall.
Cost is about $8. You’ll see the office on the main road. You must stop there first to pay and receive a bracelet. Then you can drive further in, park, and walk in. There is a checkpoint right before the waterfall to make sure you have a bracelet – so don’t forget to pay before you hike in!
The hike is about 4 km in, and 4 km back (about 2.5 miles each way). The hike is, relatively, easy (but maybe a bit long for some people).
There are restrooms and changing rooms (if you want to put on a bathing suit).