When a vessel is dredging or is involved in
underwater operations (fig. 9-26), the following light
signals are required: RED-WHITE-RED displayed
vertically, RED-RED on the obstructed side,
GREEN-GREEN on the clear side, a masthead light,
a sternlight, and sidelights. The masthead, sternlight,
and sidelights are only used when making way. The
dayshape signal is BALL-DIAMOND-BALL
displayed vertically, two black balls vertically
displayed on the obstructed side, and two black
diamonds displayed vertically on the clear side. Rule
27 applies here.
Figure 9-26.Vessels engaged in dredging or underwater operations: (A) making way; (B) not making way.