An underwater city built on granite blocks is now teeming with marine life.

Devonshire cup coral is the latest marine species to make a new home on the artificial reef within the Salcombe-Kingsbridge Estuary, further diversifying the rich marine community already in place.

During a recent dive survey by marine biologists it was discovered just how rich in marine life the reef now is. It is completely covered with life and is home to a variety of species, including sponges, anemones, sea squirts, filter-feeding worms and sea weed.

Around 360 tonnes of granite blocks were dropped onto the seabed off Scoble Point to form the artificial reef in two stages in May 2000 and November 2002.

"The reef looks more like a rockery than what most people might imagine it to look like but it does give wildlife a rich choice of surfaces, nooks and crevices," said Nigel Mortimer, South Hams District Council's Marine Conservation Officer.

"Added to the very strong tidal currents which hit the reef four times a day, bringing a rich seawater soup to be strained, sieved and filtered by the reef’s occupants - it all adds up to a very desirable residence for marine life.

"Supported by many volunteer divers over the years, we have tried to survey the reef and keep photographic records of the recruitment of life to the reef and the successional changes over time.

"The community supported by the reef is rich and diverse and can be very beautiful and colourful but I have always said that I wouldn’t be truly content with the reef until we had coral growing on it … and now we do, at least three Devonshire cup corals!"

The choice of granite as the base material was slightly controversial - one marine biologist suggested it would remain sterile and called the reef "Mortimer's Folly". Although time has proven that wrong, the name has stuck!

Early in 1987 Batson Creek was dredged to create a navigational channel accessible at all tides. Approximately 16,000 cubic metres of thick mud was allowed by licence to be dumped onto the reef site, completely smothering the important natural, habitat.

It had been that the strong scouring action of the estuary's tidal currents would erode away the dredge spoil, but a diving survey in February, 1998 discovered that small stones within the mud had been exposed forming a protective layer against further erosion.

A strong desire to right a past wrong and with support from the Kingsbridge and Salcombe Estuary Conservation Forum and local people, the artificial reef project cost just £5,000.

Funding for the reef was given by Natural England, the Devon Wildlife Trust, local scallop diver Alan House and European Regional Development Funds.

Mr Mortimer: "The artificial reef has been a great success, but I think we all agree that it is very much second best to the original habitat smothered by the dredged material.

"Such projects can be used to go some way to correct past wrongs but they should not be seen as a mitigation solution for planned damage to the seabed or marine habitats."