At first this appears to be just a small park with a boat launch, but explorers and fishers can find primitive trails to follow both upriver and downriver.
The paved paths include an approach to the river that is a good place to watch
During high water season, the trails are flooded, but when the river level is low you can explore upriver along the shore, or a primitive trail which then loops back to connect to the field north of the park. I have not fully explored the trail downriver, but it appears to connect to a peninsula on the river which extends over half a mile downriver. Be prepared to climb over logs or other obstacles and pass through brambles with thorns.
I was out at Haapa in December 2021 and found some trees being taken down by a beaver.
This park seems to be targeted toward people planning to spend the day on the river. The facilities there include a restroom (with running water) and a number of picnic tables along the edges.