We were sailing swiftly along on a calm and glassy sea, past beautiful headlands and bits of scenery clothed with vivid and luxuriant green down to the water's edge; past glistening coral islands, on whose outer edges pale green billows broke on the white sandy beaches, boiling and seething as they dashed against a row of ugly "nigger heads," as the rocks were called, dotted here and there.
Source: wiktionary