Deep-water marine caves are one of the Earth's last largely unexplored frontiers of undiscovered fauna (animal life). More than 150 limestone caves are known to exist in or near the island of Bermuda. Many of these caves have extensive but relatively shallow submerged portions that connect to the sea via tidal springs along the coastline. These inland caves are inhabited by a number of diverse eyeless and colorless crustaceans and other invertebrates. Many of these organisms are "living fossils"; and some are most closely related to deep-sea organisms. While previous investigations of marine caves have been limited to those within shallow depths (less than 50 meters/164 feet), current research suggests that caves can occur at almost any depth within the sea. The geological history of Bermuda, coupled with biological evidence (cave-adapted species), indicates a strong possibility for the presence of deep-water caves near the island. Thus, Bermuda offers an idea location to search for and to study deep-water caves.