Charts - - the Nature of the Seabed

The Nature of the Seabed  - - Symbols on Nautical Charts

When observing a nautical chart we often see symbols and letters indicating what kind of seabed could be found at certain locations.  This information is very often helpful when choosing a place to anchor.  The following descriptions are from NOAA Chart #1 - a book that lists all of the symbols used on NOAA charts.

S  =  sand

M  =  mud

Cy; Cl  =  clay

Si  =  silt

St  =  stones

G  =  gravel

P  =  pebbles

Cb =  cobbles

Rk; rky = rocks - rocky

Co  =  coral and coraline algae

Sh = shells

S/M  =  sand over mud

Wd  =  weeds

 There are also "branchy squiggles" for kelp

 And "wavey squiggles" for sand waves

Knowing what kind of bottom there is will help you determine what kind of anchor to use.  

Fluke anchors like the "Danforth" anchor are best suited for sand or sand/mud bottoms.

Hinged plow anchors like the venerable "CQR" are best suited for sand, weeds or rocks

Claw style anchors like the "Bruce or Claw" anchors are best for sand or rocks

Non-hinged plow anchors like the "Delta" are best for sand, rocks, weeds, or mud

Non-hinged scoop anchors like the "Rocna" are best suited for sand, rocks, weeds or mud

Pick your anchor for the bottom you intend to anchor in.  

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