The colour and characteristics of many of the lights and structures in the Eastern Mediterranean are still in process of change to IALA System A. Mariners are strongly advised to consult the latest charts and Notices to Mariners for up to date information.

The system provides the five types of marks described below which may be used in combination:

The significance of any mark depends upon one or more of the following features:

By night—colour and rhythm of light. By day—colour, shape, topmark.

Lateral marks used in conjunction with a conventional direction of buoyage, generally used for well defined channels. These marks indicate the port and starboard sides of the route to be followed. Where a channel divides, a modified lateral mark may be used to indicate the preferred route. Lateral marks differ between buoyage regions A and B.

Cardinal marks used in conjunction with the mariner's compass, indicate where the mariner may find navigable water.

Isolated Danger marks indicate isolated dangers of limited size that have navigable water all around them.

Safe Water marks indicate that there is navigable water all around their position, e.g. mid-channel marks.

Special marks not primarily intended to assist navigation but indicating an area or feature referred to in nautical documents.

CONVENTIONAL DIRECTION OF BUOYAGE

The conventional direction of buoyage may be defined in one of two ways:

The general direction taken by the mariner when approaching a harbour, river, estuary or other waterway from seaward, or

In other areas it is determined by the appropriate authority. In principle, it follows a clockwise direction around land masses.

The conventional direction is indicated in appropriate nautical documents.