One Long Blast

One prolonged blast of 4 to 6 seconds is the COLREGs Rule 34(e) signal a vessel sounds when nearing a bend or an area of a channel where other vessels may be hidden by an obstruction; an approaching vessel answers with the same signal. The same prolonged blast at intervals of not more than two minutes is the Rule 35 restricted-visibility signal for a power-driven vessel making way. The maneuvering signals differ: one short blast means altering course to starboard, two short to port, three short operating astern propulsion.