Swallow’s Cave in Tonga is a natural formation in the side of one of the Islands of Vava’u. Formed by volcanic activity, these beautiful islands are made of porous rock that has some very mysterious and beautiful chambers. Swallow’s Cave is one of the most famous. The narrow opening gives way to a large cavern with steep arches overhead and a deep and crystal clear bay beneath. Thousands of fish school and shimmer in the light and they create a dazzling visual effect as they dart around in the cave in response to approaching swimmers.