Free like the Pahoa Pool and although not aesthetically the nicest pool you will have swam at, it's a 50 meter x 25 yard pool and there are lots of 25 yard lanes to swim.
Typically the water is a degree or three colder than Pahoa pool. It's been as low as 70 degrees in the winter so maybe want to wear a swim shirt.
Nicest swim facility on this side of the island. Newer, lots of swim lanes if you want a good swim workout.
Check prior to going as it's not open all the time. +1 808 965 2700
I wanted to share a hiking link if you like hiking. Chain of Craters Lake in the Volcano National Park is awesome. Also, if you see Lyman on the property, ask him to recommend some local hikes not that well known.
https://www.gohawaii.com/islands/hawaii-big-island/things-to-do/land-activities/Hiking
Great local shop that can help you with stand up paddling, kayaking, diving....
My in-laws love bird watching. Here is a good site to book tours or get more info:
https://www.hawaii-forest.com/tour_category/hawaii-birdwatching-tours/
If you have water proof kids, they might like this: