Chart No. 1 · J 11
Sh — Shells
Seabed
'Sh' marks a bottom of shell fragments — moderate holding, often mixed with sand or mud.
What it means
The italic abbreviation 'Sh' marks a seabed of shells (skeletal remains), frequently charted in combinations such as 'S.Sh' — sand and shells.
Why it matters
Loose shell layers can prevent an anchor digging into the firmer material beneath. Combinations tell the real story: 'M.Sh' holds far better than plain 'Sh'.