Rising column of thirty bubbles 3.2 m tall, widening as it goes, over a small dark vent in the seabed. Dimensions 0.81 by 3.32 by 0.66 m (X by Y by Z). Metre units, +Y up, +Z front, origin on the footprint at seabed level. Modelled as solid bubbles in the pack translucent emissive material rather than as a flat card, so it reads from any angle. Static: rising bubbles are a particle system, not a rigid node transform. Sunken city palette: weathered grey limestone and dark algae stained stone, pale silt, deep green weed, coral pink, waterlogged timber, tarnished bronze and one translucent blue emissive for glow, bubbles and light. Static geometry; no rig, animation, collision or navigation data.