Experts say this small Horn of Africa nation has some of the most pristine coral reefs left anywhere worldwide, a "global hotspot" for marine diversity supporting thousands of species.

Known also as Green Island for its thick cover of mangroves, Sheikh Seid is only one of 354 largely uninhabited islands scattered along Eritrea's southern Red Sea desert coast, many part of Eritrea's Dahlak archipelago.

The remote reefs are exciting scientists, who see in Eritrea's waters a chance of hope amidst increasingly bleak predictions for the future of coral reefs -- if sea temperatures rise as forecast due to global climate change.

Unlike the deeper, cooler waters elsewhere in the Red Sea, Eritrea's large expanses of shallow -- and therefore hotter -- waters have created corals uniquely capable of coping with extremes of heat, scientists say.

"Eritrea has the most temperature tolerant corals in the world," said marine expert Dr John 'Charlie' Veron, dubbed the "king of coral" for his discovery of more than a fifth of all coral species.

"That bodes well, for climate change is set to decimate coral reefs."

Leading scientists warn that most reefs -- vital for the massive levels of marine life that depend upon them and a crucial component of coastal economies -- will be largely extinct by the end of the century unless greenhouse gas emissions are curbed.

They say many will be killed by mass "bleaching" and irreversible acidification of seawater caused by the absorption of carbon dioxide into surface waters, with at least 20 per cent of coral reefs worldwide already feared lost.

But with Eritrea's surface water in summer an average bathwater temperature of 32.5 C (90.5 F) -- reportedly peaking at a sweltering 37C (98.6 F) -- corals here have evolved to survive in an environment that would kill others elsewhere in the world.

Eritrea's isolation due to long years of bloody war with neighbour Ethiopia, combined with minimal tourist numbers and government efforts to protect the coastline, have left much of the country's extensive coral reefs untouched.

"Around most of the world, especially Asian and African coastlines of the Indian Ocean, coral reefs have been plundered in one way or another, the most damaging activity being explosive fishing," added Veron, former chief scientist with the Australian Institute of Marine Science.

"The reefs of Eritrea look as if they have been in a time warp -- they have not been touched."

On a recent three-week diving expedition along Eritrea's 3,300 kilometres (2,046 miles) of mainland and island coastline, Veron found five species new to science -- something the scientist described as "most unusual".

"Eritrea probably has the richest suite of corals of the Red Sea, and its 'coral gardens' are in exceptionally good condition," he added.

Such findings have encouraged ambitious plans offering hope for the future of reefs worldwide, with some believing that Eritrea's corals offer a potential nursery for future "re-planting".

Alain Jeudy de Grissac, a French marine scientist who has spent the past three years diving along Eritrea's coast, believes small coral buds -- comparable to taking cuttings from plants -- could be placed in areas where coral has died by sea temperature increases.

"The coral here is already well accustomed to high temperatures for long periods of time," Jeudy said, a former technical advisor to Eritrea's marine conservation body.

"If you seed the coral it would spread out... it would of course take some time, but they could occupy the area left by others."

The principle of re-seeding coral, or "ecological restoration", has already proved successful, Jeudy added.

"It has already been done in the case of accidents, such as if a ship grounds and the coral is crushed," he said.

"Testing would be needed, as this would be a totally new concept for coral reef researchers, but it could be one future of coral survival for many countries."

It also offers a potentially lucrative opportunity for tourists. Veron pointed out that just north of Eritrea, visitors to Egypt's Red Sea reefs generate more cash than visitors to its famous archaeological sites.

"The Eritrean reefs are a tourist industry gold mine waiting to be opened," Veron said.

Eritrean tourism still has far to go, hampered both by concerns of renewed conflict with Ethiopia, and reports by human rights groups that the military regime is guilty of widespread abuses.

However, the government says it is deeply committed to conservation, with Dr Woldai Futur, Eritrea's minister for national development, calling climate change the "most challenging global issue", which, if not addressed, would have "catastrophic consequences".

On Sheikh Seid, planned to be Eritrea's first marine protected area, those snorkeling over the reefs are excited by the sights beneath the waves.

"The colours are fantastic," one swimmer said, emerging out of the sparkling blue water. "The fish are all around me."

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