Pools seem adult oriented. Is there a better option for teens? Maybe one that is natural and not a municipal pool.
I saw plenty of teens and people of all ages in the thermal pools in Reykjavik. And the Blue Lagoon has all ages there - I think the minimum age is 2 years old.
Is there one in particular you found that was adult-oriented?
The Sky Lagoon in Reykjavik does not allow kids under the age of 12. Otherwise most are fine with kids. As mentioned, Blue Lagoon says 2 is the minimum age. We have also been to the Secret Lagoon, GeoSea, and Myvatn all of which have no age limits.
I actually think that the municipal pools are the better option for teens. I've been to several pools (municipal) as well as thermal spas, and the municipal pools are set up to accommodate more of the public. If you are looking in Reykjavik, just Google Reykjavik pools and you can see all the features. Some have really large pools in addition to the hot pots, many have very large slides, etc. I found a great public pool in Akureyri that had a really good slide, and yes, I did use it too!
We went to a variety of thermal pools and saw tons of families with teenagers. I wouldn't describe them as adult oriented. I wouldn't hesitate to take teenagers.
Of course, theres nothing wrong with the thermal pools for teens. My thinking on the municipal pools being more suited for your teens was two-fold. First off, many of them have slides and other features which give younger folks something to do rather than just sit in a thermal pool. The other benefit is that I think local teens are more likely to be found in the municipal pools, rather than the thermal pools which seem to draw more adult tourists. If your teens were willing to interface with people of the same age, I think it would be easier to find them in the municipal pools, just because they're more local and accessible to people not yet old enough to drive.