Retroreflectors. One or more white bands, letters, numerals or symbols of retroreflective material are used in the standard code. Red and white stripes or bands are used in the comprehensive code.

Lights. A white light, occulting, or isophase, or showing a single long flash or morse code A is used for safe water marks. If a long flash (not less than 2 seconds) is used, the period of the light is 10 seconds.

Purpose. Safe water marks are used to indicate that there is navigable water all round the mark. It could be used as a centre line, mid-channel or land fall buoy, or to indicate the best point of passage under a bridge.