Promptkoi

Underwater Reef Coloring Page

Stable Diffusion
By Varun Sharma Tested with Stable Diffusion SDXL 1.0

Underwater Reef Coloring Page is an SDXL 1.0 prompt for a printable reef scene at 3:4. Requiring every outline to be a closed shape is what stops digital fill and marker ink bleeding across the page.

Last tested: July 2026 with Stable Diffusion SDXL 1.0

Part of the Stable Diffusion prompt library · see more line art prompts .

Coloring page outline of a reef with a sea turtle, clownfish, anemone and branching corals
Underwater Reef Coloring Page — Stable Diffusion SDXL 1.0, Aspect ratio 3:4

Prompt

A coloring page line drawing of a coral reef scene, a sea turtle gliding across the centre of the frame, three clownfish among anemone tentacles, branching staghorn coral and rounded brain coral along the seabed, a few kelp fronds rising at the left and right edges, drawn in clean uniform black outlines of even weight on pure white, every shape fully closed so colour cannot leak between them, no shading, no grey fill, no hatching, no solid black areas, generous open shapes, no text

Negative prompt

blurry, low quality, shading, grey fill, cross-hatching, solid black areas, photorealistic, colour, text, watermark, broken open outlines, dense tiny detail, thin faint lines

Settings

Model
Stable Diffusion SDXL 1.0
Aspect ratio
3:4
Steps
30
CFG scale
6.5
Sampler
DPM++ 2M Karras

How to use this prompt

Closed shapes are the requirement nobody writes down and every reef page needs. Anemone tentacles and kelp fronds are exactly the forms SDXL leaves open-ended, and one unclosed outline lets a digital fill flood the entire page or a marker run out into the water. "Every shape fully closed so colour cannot leak" is the instruction that fixes it. The second control is density: reefs are intrinsically intricate, so naming three specific corals caps the detail where asking for "a reef" would bury the page in texture too fine for a child to colour.

Variations to try

  • Simplify for toddlers: one large turtle, two fish, three coral shapes, and much thicker lines
  • Swap the biome to a kelp forest with an otter, sea stars and rocky ledges in the same line style
line art whimsical coloring pages childrens book

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What to do next

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For developers — copy this prompt as JSON
{
  "title": "Underwater Reef Coloring Page",
  "prompt": "A coloring page line drawing of a coral reef scene, a sea turtle gliding across the centre of the frame, three clownfish among anemone tentacles, branching staghorn coral and rounded brain coral along the seabed, a few kelp fronds rising at the left and right edges, drawn in clean uniform black outlines of even weight on pure white, every shape fully closed so colour cannot leak between them, no shading, no grey fill, no hatching, no solid black areas, generous open shapes, no text",
  "negative_prompt": "blurry, low quality, shading, grey fill, cross-hatching, solid black areas, photorealistic, colour, text, watermark, broken open outlines, dense tiny detail, thin faint lines",
  "model": "Stable Diffusion",
  "model_version": "SDXL 1.0",
  "settings": {
    "aspect_ratio": "3:4",
    "steps": 30,
    "cfg": 6.5,
    "sampler": "DPM++ 2M Karras"
  },
  "style_tags": [
    "line-art",
    "whimsical"
  ],
  "use_case_tags": [
    "coloring-pages",
    "childrens-book"
  ],
  "source_url": "https://promptkoi.com/prompts/stable-diffusion/underwater-reef-coloring-page/"
}

The whole library is available as an open JSON dataset · developer docs.