Chart No. 1 · J 10
Co — Coral
Seabed
'Co' marks coral — a hard, fragile bottom that cuts rodes and must not be anchored on.
What it means
The italic abbreviation 'Co' marks a seabed of coral or coralline algae.
Why it matters
Coral is razor-sharp (it chafes through nylon rode fast), snags chain, and is a protected living habitat in many places — anchoring on it is often illegal as well as unwise. Find sand nearby instead.