A depiction of waves, colored black or grey in the oldest depictions. The number of ripples varies, but the ends always slant down and can sometimes be longer than the other strokes. In less careful writing, the hieroglyph can be found simplified to a single horizontal line, sometimes rising at the end. It is conventionally colored black/blue. Compare the Chinese character 巛.
The phonogrammatic value is possibly derived by the rebus principle from the word for water, nt, but this word only appears in the Middle Kingdom. An alternative source could be the older nwjt.