Safe water marks

Portuguese RBMN calls these marcas de águas limpas; English uses safe water marks. In this context clean does not mean drinking quality, freedom from pollution or visibility to the bottom. It is a system identity indicating navigable water around the mark rather than a danger. Uses can relate to mid-channel, centre-line, approaches or landfall. The figure shows recognition characteristics while separating purpose examples from any actual route. Safe in the name is not a certificate that every vessel can pass at any distance or in every water-level condition.

The body has red and white vertical stripes. One red ball is the distinctive topmark where present; the body can be spherical or pillar or spar with a spherical topmark. Compare isolated danger: two black balls and black/red horizontal bands. Compare emergency: blue/yellow vertical stripes and an upright cross. Category does not follow simply from counting colours. Stripe orientation, topmark colour and form, and the published arrangement make differences readable. The body’s recognisable spherical form and the topmark are related features rather than two identical terms.