Fathom is a fast-playing skirmish game where each player commands a three-person Dive Team consisting of a Dive Master, First Mate, and Specialist. Every game begins by generating a unique underwater mission, building a multi-level seafloor full of wrecks, elevations, Marineium deposits, dangers, and Deep Sea Threats. Your team must navigate the depths, recover valuable Marineium, and complete objectives while avoiding rival divers and the horrors lurking below. 

The core of the game is the Cost of Success system. Instead of asking whether an action succeeds, Fathom assumes your divers are skilled enough to get the job done. Skill Checks are resolved using D6 Hazard Dice, with each Hazard symbol increasing the price of success. Players must decide whether to damage their equipment, strain their dive suit, or accept the action's unique consequence to achieve their goal, creating meaningful decisions with every roll.

As the mission unfolds, your Dive Team accumulates Hazards, equipment wears down, currents and weight affect movement through the battlefield, and every decision becomes a choice between securing one more piece of Marineium and making it back to the Diving Bell in one piece.