The Maldives A lagoon with crystal clear water encircles all the islands, which are protected by a reef structure that is home to an array of underwater life.

According to 2026 global environmental rankings, Iceland is considered the island with the cleanest and highest-quality water in the world. Its tap water is sourced directly from deep volcanic aquifers and glacial springs that have been naturally filtered through layers of basalt for decades. The water is so pure that it is typically cold, untreated, and chemical-free when it reaches the tap. In the tropics, the Cook Islands (specifically Aitutaki) and the Exumas in the Bahamas are often cited for having the clearest and "cleanest" oceanic water, with visibility reaching over 100 feet deep due to a lack of runoff and pollution. For municipal purity, the island nation of New Zealand also ranks exceptionally high, with many regions providing spring-fed water that requires minimal processing. Whether you are looking at the geological purity of Iceland's glacial springs or the crystal-clear azure waters of a remote Pacific atoll, these islands represent the pinnacle of global water quality in 2026.