8 seamanship secrets
Symbols Th at Shout “Danger!” and “Beware!”
Learn to recognize rocks, coral, wrecks, and obstructions at a glance on your
chart. Some rock symbols are accompanied by the abbreviation Rk or Rky—but
not always. Here’s a quick summary of the four primary danger categories you’ll
want to become familiar with:
ROCKY ROADS
Plus sign. Dangerous rocks that lie underwater at all stages of the tide. Avoid
these hazards like the plague.
Plus sign with dots. Dots in all four corners of the plus-sign symbol
indicate rocks that are barely visible, or just awash, at MLLW or LAT.
Asterisk or squiggly-edged, rounded shape, accompanied by underlined number.
Th ese rocks cover and uncover with the tide. Th e symbol is usually accompa-
nied by an underlined number to indicate height above the low-water datum.
SEA-CRET TIP
X U.S. federal law requires vessels with easily lowered antennas to
lower them before requesting a bridge opening. That’s another reason
to always know the “antenna-up” and “antenna-down” height of your
vessel.Th is chart detail shows the symbol for rocks that lie underwater at all stages of the tide.