Why pools?
Swimming is an essential part of Icelandic culture, which is also why every town has at least one public pool. This is because of the huge geothermal water deposits that the county has, making a warm water pool an easy facility. But swimming isn't all, as there are a multitude of other activities that can be enjoyed at the Icelandic pools. Some of the other amenities the Icelandic pools have to offer are: Waterslides (which are only open in the summer), steam baths, saunas, and even ice pots.
All of the details for pools inside Reykjavík city can be found on the official Reykjavík website: (https://reykjavik.is/en/swimming-pools) which also has an English version. On a side note, for all the pools listed on the website, you can get a card with tickets which will work at all of these locations, and this is generally a better deal than buying tickets individually, but for children up to 15 years old, entry is free, and you can just ask for a ticket.
Pool etiquette:
There are two very important rules that need to be followed when going to an Icelandic pool:
Number one: Wash off without a swimsuit before entering the pools. This keeps the pools clean and makes it an enjoyable experience for everyone.
Number two: No phones in the locker rooms. This should be self-explanatory after the first rule.