Marine Wetland Codes - National Wetlands Inventory Habitat Classification: 

SYSTEM              SUBSYSTEM        CLASS                     SUBCLASS

                                  |- RB=Rock Bottom            1=Bedrock
                                  |                            2=Rubble
                                  |
                                  |- UB=Unconsolidated Bottom  1=Cobble-Gravel
                                  |                            2=Sand
                                  |                            3=Mud
                                  |                            4=Organic
                                  |
                |-- 1=SUBTIDAL----|- AB=Aquatic Bed            1=Algal
                |                 |                            3=Rooted Vascular
                |                 |                            5=Unknown Submergent
                |                 |
                |                 |- RF=Reef                   1=Coral
                |                 |                            3=Worm
                |                 |
                |                 |- OW=Open Water/Unknown Bottom (used on older maps)
M=MARINE--------|
                |
                |                 |- AB=Aquatic Bed            1=Algal
                |                 |                            3=Rooted Vascular
                |                 |                            5=Unknown Submergent
                |                 |
                |                 |- RF=Reef                   1=Coral
                |-- 2=INTERTIDAL--|                            3=Worm
                                  |
                                  |- RS=Rocky Shore            1=Bedrock
                                  |                            2=Rubble
                                  |
                                  |- US=Unconsolidated Shore   1=Cobble-Gravel
                                                               2=Sand
                                                               3=Mud
                                                               4=Organic