Fathom is a tile-laying, pattern-building game of deep-sea exploration in which you take on the role of marine biology teams competing to uncover the secrets of an uncharted, underwater ecosystem around a fictional island. The depths are vast and time is limited, so savvy decision-making under pressure is crucial to a successful expedition. Choose wisely which creatures to investigate as those you don't pursue may be discovered by your opponents. Over six rounds of simultaneous play, guide your team's boat and submersible across the ocean. Scan the unmapped depths, and place tiles representing signs of marine life. Descend into the darkness and reveal these tiles to discover remarkable creatures. At game's end, you gain points based on the scoring criteria of species you've discovered. Some thrive in a homogenous environment; others fare better surrounded by diversity. The solitary life may suit certain creatures, but straying from the safety of a group spells disaster for others. Discover the most synergistic ecosystem to win!