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As more and more people experience the delights of the underwater world - estimates put the total as high as five million world-wide and growing at the rate of 500,000 a year - the protection of the sights and eco-systems we all enjoy and like to photograph is paramount, especially in tropical waters.

Sadly, the evidence can be seen at all the popular sites as careless or incompetent divers damage corals that might have been growing for many hundreds of years. Now a system of teaching precision buoyancy control which is new to the UK and North America will enable divers of all types to test and improve their techniques.

Aptly named Diamond Reef, the equipment is being imported by Ocean Optics, the underwater photographic specialists.

As divers hover and perform other maneuvers within the confines of the 'diamonds', the system hones up their skills or reveals just how much they are in need of improvement. Diamond Reef takes the boredom out of practicing buoyancy control."

Every diver and every underwater photographer needs these skills. None of us who enjoy going beneath the waves wants to see fragile eco-systems damaged in any way. My hope is that Diamond Reef will make a positive contribution to the protection of marine life and scenery throughout the world.

The system, which is described as the world's first structured underwater education program to preserve coral reefs and improve diver training, uses diamond shaped, buoyant Rover Stations set at different depths and tests divers' buoyancy control and maneuvering skills. The Hover Stations are easy to assemble and collapse down to fit in a convenient, easy to carry holdall. They fix to normal diving weights placed on the pool bottom or the seabed and the depth at which they are suspended can be varied.

A satisfactory level of proficiency is marked by a distinctive stamp to go in log books and also a T-shirt bearing the same illustration as the stamp. The date of issue reminds the recipients that they have to upgrade their skills on an annual basis to remain 'in test'.

The programme was designed by Pete Wallingford, an educational technologist based in Seattle, Washington, US. The system is used by the US government and in over seven countries world-wide. Over 80 per cent of the proceeds from the sale of the Diamond Reef stamp is spent on educating diving instructors, their students, traveling divers and snorkellers throughout the world.

Said instructor Michael Hamilton: The system has proved to be an invaluable training aid. It allows novice divers to practice their buoyancy skills in the safety of a swimming pool so that, by the time they get into open water, they have a high degree of proficiency.

It is vital they have mastered good buoyancy skills before they dive on delicate coral reefs.