Domain: Natural Science — Marine Science
Target concept: Cold, salty water sinks in a clear tank due to increased density.

Video generation prompt: A small amount of cold, blue-colored saline water was gently released into a transparent aquaria filled with room-temperature freshwater, using a thin tube near the water surface on one side.

Evaluation guide:
(i) Target concept: Density-driven gravitational sinking of cold, saline fluid in a less-dense ambient fluid.
Minimum mechanism: The blue liquid must be denser than ambient freshwater (achieved by salinity + cold temperature), and must be introduced gently to avoid kinetic energy overwhelming buoyant force; ambient fluid must be quiescent and transparent to reveal descent path.
(ii)Storyline: [Frame 1] Tube tip positioned near surface on one side, freshwater visible in background. → [Frame 2] Blue liquid emerges from tube as continuous stream, contacting surface. → [Frame 3] Blue mass begins downward motion, retaining shape and color. → [Frame 4] Blue mass descends vertically with sharp leading edge, no breakup or rise. → [Frame 5] Blue mass reaches aquarium floor, accumulating as distinct layer. Perspective: Fixed frontal view, full aquarium in frame, no obstructions, side-of-aquarium placement visually unambiguous (e.g., tube on left, open right side visible). Visibility: Entire descent path must remain in view; no occlusion by tube, walls, or bubbles.

Manual:
Experimental Procedure
1. Fill a transparent aquarium with room-temperature freshwater until ~80% full.
2. Load cold, blue-dyed saline water into a thin rigid tube.
3. Position tube tip just below freshwater surface on one side of aquarium.
4. Gently release blue saline water — no stirring or pouring.
Observation of Experimental Phenomena
A coherent blue column descends vertically from the release point near the surface, maintaining sharp boundaries and distinct color, sinking to the bottom without significant lateral spread or immediate mixing.
Summary of Experimental Principles
Cold, salty water has higher density than room-temperature freshwater, causing it to sink when gently introduced at the surface.

Prompt Grounding rubric:
level_1: No transparent aquarium is shown; no thin tube appears; no blue-colored liquid appears; no freshwater background is visible; nothing shows a release action; the scene has nothing to do with pouring a dense liquid into a tank of water.
level_2: A transparent aquarium is present, but either the thin tube or the blue liquid is missing; or a tube is shown without any blue liquid; or blue liquid appears but isn't released from a tube near the surface (e.g., it's dropped in from above, or poured in from the bottom/middle of the tank).
level_3: A transparent aquarium holds clear freshwater; a thin tube sits near the water's surface on one side; blue-colored liquid comes out of the tube into the aquarium, starting at or just under the surface, matching the prompt's objects and action, but it isn't clear which side of the aquarium the tube is on (no obvious left/right reference in frame).
level_4: Everything in the 3-point description holds, and in addition the blue liquid comes only from the tube, positioned near the surface on a clearly identifiable side of the aquarium; the aquarium stands upright and still, fully see-through; nothing extra (hands, labels, overlays) appears in frame; the release clearly originates from the tube alone.
level_5: Everything in the 4-point description holds, and in addition the tube reads as visibly slender and rigid; the blue liquid leaves the tube as one continuous stream rather than drops or spray; the aquarium's walls show no distortion or glare that would hide the interior; the camera's fixed frontal framing makes the tube's side (e.g., left, with the opposite side clearly open and visible) unambiguous; nothing blocks the view and there are no visible cuts.

Scientific and Causal Correctness rubric:
level_1: The blue liquid stays at the surface or floats up; it spreads out sideways instead of sinking; it mixes into the freshwater right away and evenly; there's no sign of it sinking due to being denser; its blue color fades or shifts as it moves; there's no visible contrast between it and the surrounding water.
level_2: The blue liquid does sink, but as scattered drops or a churned-up plume rather than a coherent mass; it forms upward swirls or surface ripples that don't fit a gentle release; it visibly fades or dilutes before reaching the halfway point of the tank; or it rises back up after first sinking.
level_3: The blue liquid sinks continuously from where it enters near the surface toward the bottom; it keeps its blue color the whole way down; it forms one coherent, wedge- or column-shaped mass moving downward; it stays visibly distinct from the surrounding clear water for at least two-thirds of its descent; the descent looks smooth and roughly straight down.
level_4: Everything in the 3-point description holds, and in addition the descending blue mass stays in one piece (it doesn't break into separate blobs or streams); it doesn't spread sideways or drift upward instead of sinking; the contrast between the blue liquid and the freshwater stays strong and steady; sinking starts right after release and continues without stopping or reversing.
level_5: Everything in the 4-point description holds, and in addition the bottom edge of the descending mass stays sharp rather than trailing off into haze; its top stays roughly aligned with where it entered the tank; the color boundary between the blue liquid and the freshwater stays crisp with no visible blending along the way; the whole descent happens in the same vertical plane visible on camera, undisturbed by any stray current.

Spatiotemporal Consistency rubric:
level_1: The aquarium disappears and reappears; the blue liquid jumps straight from the surface to the bottom with no path in between; the room's lighting flips instantly from one look to another partway through; the camera cuts or zooms abruptly; the tube or liquid flickers in and out; the background changes between frames.
level_2: The aquarium stays visible but its walls warp, its reflections flip inconsistently, or its transparency fails (walls looking briefly opaque or mirror-like); the blue liquid's descent has visible gaps (frames missing from its fall); the motion stutters or skips; the lighting's direction or brightness shifts partway through the descent for no reason.
level_3: The aquarium stays visible the whole time, in the same position and orientation; the blue liquid shows up at the release point and moves downward without ever jumping; the lighting stays the same from frame to frame; nothing breaks structurally (the tube stays attached, nothing clips through the aquarium walls); the motion is continuous with no freezing or skipping, even if its speed or edge sharpness isn't perfectly even.
level_4: Everything in the 3-point description holds, and in addition the blue liquid's descent speed stays even, without sudden speed-ups, slow-downs, or jitter; the aquarium's shape stays undistorted in every frame; shadows and highlights stay in the same place relative to the scene (no floating shadows, no light source that seems to move); nothing shifts out of alignment between frames as if the camera had moved.
level_5: Everything in the 4-point description holds, and in addition the motion throughout looks physically natural, with no strobing, ghost trails, or jagged edges; the aquarium's edges stay crisp and steady; the water's surface stays flat and undisturbed except right where the liquid enters; no frame is duplicated, and nothing about the pacing feels sped up or slowed down; the camera's framing stays perfectly fixed with no drift.