Seabed Abbreviations on Nautical Charts
Codes describing the nature and characteristics of the seabed.
Common seabed abbreviations include S sand, M mud, Cy clay, Si silt, St stones, G gravel, P pebbles, Cb cobbles, R rock, Co coral, Sh shells and Wd or Wds weed. Qualifiers may describe size, colour or consistency; single letters are context-dependent.
