How to find all clusters of forest on map ? I have simple class cell like (Type is enum {RIVER, FOREST,GRASS,HILL}

class Cell{
   public:
     Type type;
     int x;
     int y
};

and map like vector<Cell> grid. Can anyone suggest me algorithm to create list<list<Cell>> clusters where list contains FOREST cells in same cluster (cluster are set of connected cells - connection can be in eight direction:up,down,left,right,up_right,up_left,down_left,down_right)? I need to find all clusters of forest on map and put every single cluster in list<Cell>.