Blue Lagoon is highly recommended, at least once if you're visiting Iceland anyway.<br><br>On an unrelated note, 'waste' water from Nuclear power plants <b>should</b> be safe as well. They're also using heat exchangers, so the water they dump never actually gets in direct contact with anything radioactive. This isn't an endorsement to go swimming though, at least not without a Geiger counter.,(reply>), Well technically, you could go for a swim in a nuclear power plants waste pool, and be perfectly fine as long as you stay in the upper half of the pool,(reply>), to quote the relevant xkcd, swimming in the upper layer of the water body, where decommissioned uranium rods are stored is safer the the surrounding air in a sense of radioactivity speaking,(reply>), The US has recreational lakes that are also used for cooling nuclear plant wastewater. Perfectly safe. There was one a few miles from my hometown.,(reply>), Ya, use to swim in a lake where the nuclear plant would cycle its heated water. Uncanny to have a slight chill in the air but the lake was very much warmer than a swimming pool.,(reply>), @Rou Lor You are correct - for a pressurized water reactor - there are three loops - primary (reactor side), secondary (seam and water that runs the turbine) and the cooling loop (cools and condenses the turbine exhaust steam). This is a very simplified explanation.