Whipped this up over my lunch break. Still need to test it more extensively, but take a look and tell me if you see any glaring errors.
The desired effect is for Driftwood "vermin" to wash up on shore, leaving behind un-butcherable corpses that are instead automatically processed at a Wood Furnace to "dry" them into usable logs - or sometimes furniture - to help the beleaguered tree-deprived ocean embark.
In object:creature;
[CREATURE:DRIFTWOOD_CREATURE]
[DESCRIPTION:A tangled mass of seaweed and wooden debris.]
[NAME:driftwood:driftwood:driftwood]
[CASTE_NAME:driftwood:driftwood:driftwood]
[CREATURE_TILE:22][ALTTILE:126][COLOR:6:0:0]
[PETVALUE:1]
[AQUATIC][BEACH_FREQUENCY:99]
[VERMIN_GROUNDER][VERMIN_FISH]
[SMALL_REMAINS][NOBONES][IMMOBILE_LAND][VERMIN_NOTRAP][VERMIN_NOFISH]
[NO_THOUGHT_CENTER_FOR_MOVEMENT]
[NOT_BUTCHERABLE]
[NOPAIN]
[NOEXERT]
[NOEMOTION]
[NOFEAR]
[NATURAL]
[MUNDANE]
[BIOME:OCEAN_ARCTIC]
[BIOME:OCEAN_TEMPERATE]
[BIOME:OCEAN_TROPICAL]
[UBIQUITOUS]
[POPULATION_NUMBER:50:100]
[CLUSTER_NUMBER:5:10]
[BODY:BASIC_1PARTBODY] *** lazy!
[TISSUE:WOOD]
[TISSUE_NAME:wood:wood]
[TISSUE_MATERIAL:PLANT_MAT:WOOD_DRIFTWOOD:STRUCTURAL]
[MUSCULAR]
[FUNCTIONAL]
[STRUCTURAL]
[RELATIVE_THICKNESS:1]
[CONNECTS]
[TISSUE_SHAPE:LAYER]
[TISSUE_LAYER:BY_CATEGORY:ALL:WOOD]
[APPLY_CREATURE_VARIATION:STANDARD_SWIMMING_GAITS:9000:8900:8825:8775:9500:9900] 1 kph
[MAXAGE:20:30]
[ALL_ACTIVE]
[NO_DRINK]
[NO_DIZZINESS]
[NO_FEVERS]
[SWIMS_INNATE]
[CANNOT_JUMP]
In object:reaction;
[OBJECT:REACTION]
[REACTION:PROCESS_DRIFTWOOD]
[NAME:Dry driftwood]
[BUILDING:WOOD:NONE]
[REAGENT:A:1:REMAINS:NONE:DRIFTWOOD_CREATURE:NONE]
[PRODUCT:100:1:WOOD:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:20:1:BED:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:15:1:BUCKET:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:15:1:BARREL:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:10:1:SHIELD:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:5:1:TABLE:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:5:1:CHAIR:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:5:1:ARMORSTAND:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:5:1:WEAPONRACK:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:5:1:DOOR:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[PRODUCT:5:1:FLOODGATE:NONE:PLANT_MAT:WOOD_DRIFTWOOD:WOOD]
[SKILL:WOOD_BURNING]
[AUTOMATIC]
[DESCRIPTION:Cleans and dries washed-up driftwood, yielding logs or other items. Driftwood can be found on beaches.]
In object:plant;
[OBJECT:PLANT]
[PLANT:WOOD_DRIFTWOOD]
[NAME:driftwood][NAME_PLURAL:driftwoods][ADJ:driftwood]
[USE_MATERIAL_TEMPLATE:STRUCTURAL:STRUCTURAL_PLANT_TEMPLATE]
[DISPLAY_COLOR:6:0:0]
[BASIC_MAT:LOCAL_PLANT_MAT:STRUCTURAL]
[USE_MATERIAL_TEMPLATE:WOOD:WOOD_TEMPLATE]
[STATE_NAME:ALL_SOLID:driftwood]
[STATE_ADJ:ALL_SOLID:driftwood]
[PREFIX:NONE]
[STATE_COLOR:ALL_SOLID:BROWN]
[DISPLAY_COLOR:6:0:0]
[SOLID_DENSITY:600]
[TREE:LOCAL_PLANT_MAT:WOOD][TREE_TILE:5]
[TRUNK_PERIOD:10]
[HEAVY_BRANCH_DENSITY:0]
[BRANCH_DENSITY:50]
[MAX_TRUNK_HEIGHT:8]
[BRANCH_RADIUS:2]
[TRUNK_BRANCHING:0]
[MAX_TRUNK_DIAMETER:1]
[TRUNK_WIDTH_PERIOD:200]
[STANDARD_TILE_NAMES]
[TREE_COLOR:6:0:1]
[DEAD_TREE_COLOR:0:0:1]
[SAPLING_COLOR:6:0:1]
E
[DEAD_SAPLING_COLOR:0:0:1]
The plant/wood related bits are what I'm most concerned about, as I had a hard time finding any raws that produced wood items without using GET_MATERIAL_FROM_REAGENT. I assume I need a dummy "tree" that doesn't grow anywhere to properly store driftwood logs in stockpiles, right?
EDIT: Updated reactions so that they output correctly now, and adding [UBIQUITOUS] to the Driftwood "creature" ensures it shows up - also BEACH_FREQUENCY to 99.
EDIT2: Added NOEMOTION/FEAR/EXERT just in case, and finally got the material/tissue definition to stop spitting errors at me. Changed creature name and reaction name call for clarity.
EDIT3: Welp, I'm giving up for now. I can't get the driftwood vermin to wash ashore on the beach, regular fishing doesn't work, and butchering to logs is a no-go... so I'm gonna shelf it for now for sanity's sake. If anyone else can make it work, feel free.