Lost In Reefs is a game in the match-3 genre set in an undersea world. The story of the game goes that the player has found ancient scrolls that proved the existence of dragons. Unfortunately, a powerful earthquake destroyed the dragon city; the tremors were so great that the city sank to the bottom of the ocean. Players then go on an expedition to search for and rebuild the dragon city. To uncover the secrets that would lead them to the ancient city, players must first solve puzzles by matching at least three pictured objects of the same kind. To finish a level, they must be able to break marble tiles by first breaking the tiles positioned atop them.
Lost In Reefs has three different matching modes: group, swap, and chain. In Group mode, players must click on groups of three or more items of the same kind to create matches. In Swap mode, players can swap two adjacent items to line up three of the same type. In Chain mode, matches are made by clicking and dragging the mouse over the tiles containing items of the same type. Players can also select the field type they want to play in. It can be a square, a hexagon, or a mixture of both. The game provides players with bonuses and power-ups to help them break the marble plaques.