I was in Iceland in 2015 and looked at going to the Blue Lagoon. The trouble was you have to reserve way ahead of time and it was 35 Euros for admission. Instead, so I could say I swam in a geothermal heated pool, I went to the Vesturbæjarlaug public pool, about 1.4 Km from downtown Reykjavik. The admission was about 4 Euros and it was much easier to get to.