Modifiers matching obstruction:

• structural,
• discrete,
• permanent,
• physical,
• outdoor,
• linear,
• significant,
• opaque,
• temporary,
• subsurface,
• tall,
• solid,
• dense,
• vertical,
• typical,
• topical,
• large,
• local,
• minor,
• hydraulic,
• spatial,
• raised,
• hard,
• virtual,
• overhead,
• underwater,
• horizontal,
• nearby,
• short,
• visual,
• artificial,
• cooler,
• current,
• multiple,
• environmental,
• unusual,
• hazardous,
• lateral,
• impenetrable,
• underground,
• geographic,
• urethral,
• natural,
• movable,
• larger,
• nasal,
• rigid,
• terrestrial,
• upright,
• level,
• immovable,
• fixed,
• lighted,
• metal,
• small,
• simple,
• smaller,
• past,
• up,
• insurmountable,
• low,
• bigger,
• isolated,
• major,
• adjacent,
• electrical,
• internal,
• over,
• under,
• relevant,
• clear,
• mechanical,
• irregular,
• additional,
• removable,
• taller,
• external,
• layer,
• elongated,
• indoor,
• surrounding,
• hidden,
• visible,
• common,
• featureless,

Simple categories matching underwater:

• part,
• object,
• substance,
• job,
• structure,
• operations,
• area,
• gear,
• disturbance,
• creature,
• surface,
• information,
• prey,
• article,
• unit,
• plant,
• organism,
• task,
• artifact,
• worker,
• craft,
• predator,
• appendage,
• construction,
• grass,
• vehicle,
• mound,
• heritage,
• obstruction,
• munition,
• service,
• animal,
• explosive,
• ordnance,
• cetacean,
• happening,
• feature,
• wonder,
• activity,
• instrumentation,
• mammal,
• weaponry,
• system,
• mission,
• cave,
• substrate,
• duty,
• shape,
• world,
• work,
• missile,
• weapon,
• location,
• function,
• shock,
• resource,
• facility,
• formation,
• sport,
• prop,
• projection,
• life,
• means,
• metal,
• operation,
• event,
• vessel,
• use,
• material,
• equipment,
• body,
• installation,
• experience,
• inhabitant,
• connection,
• killer,
• native,