| The map is based on grain size distribution and indicates how easy it would be to dig into the sea floor, and how stable the dugout depression would be. |
| Symbol | Diggability | Sediment type | Code |
|---|---|---|---|
| Diggable, stable trench | Fine-grained sediments with high content of clay and silt | 1 |
| Diggable, unstable trench | Sandy and gravelly sediments | 2 |
| Hardly diggable | Coarce-grained sediments, stony bottom | 3 |
| Not diggable | Exposed bedrock or thin sediment cover on bedrock | 4 |
| NGU | Mareano |