We’re continually surprised at what boaters don’t see when they’re charting a course or looking for an anchorage on the GPS or on a paper chart. You’d be surprised at the number of recreational skippers who think that fish bone symbol means it’s a fishing spot (often it is, but that’s a separate conversation).
What that really means is a shipwreck on the bottom. And, the form of the symbol is an indication of navigability – is it relatively safe to sail near or even over the wreck? Since boating safety is a paramount concern, this is something we all need know about sailing, and keeping the StaPlug, the raft and PDF dry.
On the left-hand chart, you’ll see two wreck symbols, and both are safe to sail across. The remains of the wreck are minimal, and they are in relatively deep water. However, you’ll want to be careful anchoring, as you could foul your and anchor or rode.
In the center, you’ll see the symbols with a dotted outline. That means STAY AWAY. Those wrecks are shallow enough to be a danger to your vessel. You’ll note that the lower wreck even has a notation “Mast”, meaning that the mast is above the surface at low water.
On the right is the symbol showing a semi-submerged hull on a reef. That one is self-explanatory – the wreck is at the surface, and is visible. Without knowing tide and current, the simple solution is to stay out around the 90-foot line. Since it’s not lighted, basic navigation applies (A cross bearing on the nearest lighted marks and a close check on the depth sounder).
Check the chart before you go in there, and plan/plot a course clear of the hazards. A little care will help you not be another symbol on the chart.