Sailing Navigation Secrets - Do You Know These Sea Bottom Chart Symbols?

Do you know which chart symbols describe the best type of sea bottom for anchoring? Would you rather anchor in rock, mud, coral, or clay? If you go aground, would it be safe to back off of a shoal or could that action punch a hole in your boat? Learn the secrets of the sea bed to help you make these vital decisions.

Your navigational chart breaks sea bed characteristics down into type, texture, and color. You will always see the type of bottom on your chart. Texture or color is often shown to give you a better description of the bottom type.

Type of the Bottom

Choose a hard mud or clay bottom for the best, worry-free overnight anchorage. Your boat anchor could drag in bottoms that indicate grass, kelp, rock, or oyster beds. Use a larger plow anchor, like a CQR, Bruce, Rocna, or Delta, or put out two anchors in bottom types like these.

Texture of the Bottom

Is the bottom texture soft, hard, sticky, or broken? Grounding isn't such a concern in soft sand, soft or sticky mud, kelp, or grass. But rock, coral, or boulders could puncture the hull, damage the keel, rudder, propeller shaft, or propeller. Use great caution not to back off of a hard shoal before you check, patch, and repair any damages.

Color of the Bottom

Color isn't used as much today, but it was vital in the days of the old square riggers. They would take samples of the bottom when approaching landfall along a fog-shrouded coast. Savvy sea captains could tell how far off land they were by looking at the color of the bottom material. Know the colors below in case you see them on your navigation chart.

Learn these common abbreviations used throughout the cruising world. Note that sea bottom symbols are always italicized on your chart:

Type

S--Sand; M--Mud; Sh--Shells; Grs--Grass; K--Kelp; Rk or Rky--Rocky; Co--Coral; Oys--Oysters; Bld--boulders.

Texture

f or fne--fine; bk or brk--broken; sy or stk--sticky; so or sft--soft; h or hrd--hard.

Color

wh--white; bl or bk--black; yl--yellow; lt--light; dk--dark.

Boost your sailing navigation skills to the next level by becoming more "sea-bottom" savvy. Know these chart symbols to give you the confidence to make the best decisions for your small cruising boat and sailing crew.