The Blue Grotto, located on the south coast of Malta's main island, is a sea cave carved into limestone cliffs. A small boat passes through the narrow opening, where sunlight streams in through gaps above the water, turning the seawater a deep blue-green. The boatman will moor the boat deep inside the cave, allowing you to see the outlines of the underwater rocks. When the waves are high outside, the boat will rise and fall with the surge. This tour is relatively short, lasting about ten minutes, but on a clear day, you can truly see the rare colors. The tour duration is greatly affected by sea conditions, so it's recommended to inquire about boat availability in advance.