INT 1 · K 40
Obstruction (Obstn)
DangersCore
Obstn identifies a submerged object that is not classified as a rock or wreck.
What it means
The abbreviation 'Obstn', with a sounding where known and a danger surround where appropriate, marks an underwater obstruction of uncertain or miscellaneous character.
Why it matters
The dotted surround marks the position symbolically rather than defining a safe passing distance. Use the chart scale and all nearby depth information.