Boating and Sailing.pdf - Moja ladja

By the way, depth-indication or “hydrography,”
as the chart-makers call it, is not necessarily
updated regularly in areas where commercial
ocean traffic never travels. Thus, some of the
shallow areas that are very attractive to boaters
and anglers may display depths that were last
ground-truthed—by sending in a boat with a
depth finder or sounding lead—50 years ago.
So always take chart depths with a grain of salt, so
to speak. This is particularly true around all inlets,
where depths can change due to storm waves and
currents from day to day, let alone year to year.
The Color of Water
Chapter 11: Nautical Road Maps: Marine Charts
Charts are printed in color, not to make them pretty as wall-hangings in your beach house
(although many wind up that way) but to convey navigational information. Here’s what
the colors mean:
◆ White: Water deeper than 3 fathoms (18 feet), safe for navigating most any recreational
boat.
◆ Light blue: Water deeper than 1 fathom but not more than 3 fathoms. Still safe for
anything but large yachts or keeled sailboats.
◆ Medium blue: Water 1 fathom or less, potentially dangerous for larger recreational
boats.
◆ Light greenish-tan: Shoals that sometimes uncover at low tide—good for fishing,
bad for boating.
◆ Light tan: Sandbars and oyster bars that go dry at low tide—very dangerous spots if
you’re not an oyster or a crab. (Also used in Florida for low-lying coastal land currently
inhabited by lots of people, but that will be inhabited by fish after the next
major hurricane.)
◆ Medium tan: High, dry land, terra firma, where your boat will be if you don’t keep
a sharp watch on the chart and the horizon.
◆ Magenta: Navigational information—danger zones and markers. Red navigational
markers are designated in magenta on the chart.
◆ Dark green: Green navigational markers.
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Look Out!
Inshore charts usually
show depths in feet. Offshore
charts often show depths in fathoms.
One fathom equals six feet.
Make sure you know which form
is being used in the chart you’re
depending on to keep you from
going aground.