ESTUARIES : The slots in the very top row on your ocean mat are estuaries. These represent the tidal mouth of a large river, where the saltwater sea or ocean meets freshwater. This creates brackish water, saltier than freshwater, but not as salty as seawater. Some marine life can thrive in brackish water, or even freshwater. Some fish cards in future expansions may only be played here, but you can place any Sunlight Zone fish here.
DEEPWATER : Some fish can thrive at extreme depths. This icon indicates the slots in the very bottom row of your ocean mat. Some fish cards may only be played here, but you can place any Midnight Zone fish here.