Þingvallavatn & Geothermal Lakes

Beyond the famous Silfra fissure, Iceland's volcanic rift zone hides a constellation of extraordinary freshwater dive sites accessible from Reykjavík. Þingvallavatn — Iceland's largest natural lake — holds additional fissures and lava chimneys beyond the main tourist corridor, populated by genetically unique Arctic char morphs found nowhere else on Earth. Kleifarvatn on the Reykjanes Peninsula is a geothermally active crater lake where hot springs bubble up through the sediment floor and sulphurous vents alter the chemistry around them. All sites share the same optical clarity of filtered Icelandic groundwater: visibility routinely exceeds 50 metres, making these among the clearest freshwater dive sites on the planet. Water temperatures hover near 2 to 4°C year-round, demanding drysuit certification and making every dive an extreme cold-water experience.