Chart No. 1 · J 1
S — Sand
Seabed
The italic letter S on the seabed means sand — generally good holding for an anchor.
What it means
An italic 'S' printed on the water area gives the nature of the seabed there: sand. Lower-case prefixes qualify it — 'fS' fine sand, 'cS' coarse sand.
Why it matters
Sand is usually good anchor holding once the hook digs in. Bottom-nature letters cluster around designated and popular anchorages for exactly this reason.