Some lights have sectors of a particular color (usually formed by colored panes in the lantern) to distinguish safe water areas from dangerous shoals.

By 1894, shallow and dangerous shoals put an end to steamboating.

Scuba diving aside, the promontory was also well-known for its dangerous shoals and strong currents.

There were dangerous shoals by Aboukir, and a long sandbank ran parallel to the strand.

But to someone unfamiliar with its shoals, very dangerous.

Or did they rely on the dangerous shoals to keep them safe?

There are many dangerous shoals at the entrance to the bay.

It is surrounded by a maze of dangerous shoals.

It is as if the ship's captain were taking on the night watch through dangerous shoals.

The light was established in 1848 to warn ships of the dangerous shoals that lie off its coast.