The main attraction of the island of Andros in the Bahamas is the Blue Holes, deep blue underwater sinkholes that appear ink-blue due to their depth. The island of Andros is part of an archipelago and is made up of small islands and coral reefs connected by passages. It is about 160 km long and 65 km wide, surrounded by warm seas except for its east coast which opens onto the Tongue of Ocean. When viewed from above, the dark blue stains of the Blue Holes are visible, which are entrances to an underground network of flooded caves and passages below the island.