The government of the Maldives is to hold a cabinet meeting underwater to highlight the threat of global warming.
President Mohamed Nasheed and his cabinet will sign a document during the 17 October dive, calling for global cuts in carbon emissions.
An adviser to the president told the BBC the dive was "a bit of fun" but the cabinet intended to send a serious message about rising sea levels.
The low-lying island nation says it faces being wiped out if oceans rise.
The adviser, who asked not to be named, said ministers would communicate during the meeting using hand signals and waterproof boards and pens.
"Obviously the hand signals that divers can use are limited, so the amount of work the cabinet are going to get done will be limited," he said.
"But they will call on all nations - rich and poor, developed and developing - to take climate change seriously."
All cabinet members bar one - who has a medical condition that rules out diving - have been in training at a military base on one of the country's many islands.
Mr Nasheed, who is already a qualified diver, will also hold a press conference in the water.
While underwater, the government will sign a document ahead of the UN Climate Change Conference in Copenhagen in December, calling on all nations to cut down their carbon emissions.
World leaders at the summit are aiming to create a new agreement to replace the 1997 Kyoto Protocol, which expires in 2012.
'Friendly' sharks
The dive is being held to mark the 350 International Day of Climate Change Action on 24 October.
The day's organisers say they want to highlight the risks of rising carbon in the atmosphere and encourage world leaders to commit to reducing carbon dioxide levels in the atmosphere to 350 parts per million.
That is the amount some scientists say is the safe upper limit to avoid irreparable damage to the environment.
Some 80% of the Maldives archipelago is less than a metre above sea level and is extremely vulnerable to any rise in sea levels as a result of global warming melting the polar ice caps.
Officials say that by the time the Maldives feels the full effect of climate change, it will be too late to save other countries.
Mr Nasheed has warned that the entire nation may have to find a new home if the oceans rise as predicted by the UN.
The president's adviser told the BBC that although the country's government was almost all going to be underwater at the same time, there was no real danger.
Each minister will be accompanied by a diving instructor and a military minder and the local sharks were "friendly", he said.
by Olivia Lang
Maldives leader in climate change stunt
With fish darting amongst them in a blue lagoon, the Maldivian president and his top team have staged an elaborate stunt to publicise climate change.
Billed as the world's first underwater cabinet meeting, President Mohamed Nasheed and 11 ministers, decked in scuba gear, held a meeting 4m (13ft) underwater.
While officials said the event itself was light-hearted, the idea is to focus on the plight of the Maldives, where rising sea levels threaten to make the nation uninhabitable by the end of the century.
Mr Nasheed, the country's first democratically elected president, has become an important global voice for climate change since he won in polls last October.
"We have to get the message across through a course of action which resonates with ordinary people," the president said, as the boat neared our destination."What we are trying to tell the people is that we hope there is a better deal at Copenhagen."
The presidential speedboat took 20 minutes to arrive in the turquoise lagoon off Girifushi, in North Male atoll.
The cabinet then zipped themselves into diving suits and donned goggles and tanks of compressed air before jumping in the water.
Major Ahmed Ghiyaz, the co-ordinator from the Maldivian National Defence Force (MNDF), said all measures had been taken to protect the president, which included checking the coral for dangerous creatures.
"I am 99.9% sure there will be no harmful creatures," he told the BBC before the dive.
"I'm sure there won't be any sharks. The nastiest thing would be a moray eel, but we have checked the reef".
A horseshoe-shaped table was set up around a dark green coral reef with blue tips and home to an array of sea creatures in one of the world's most famed diving spots.
The president and his team took their seats at 1000 at the bottom of the lagoon, sitting at desks with name tags while colourful parrot fish and black and white damsel fish darted around them.
Using hand signals to gesture that they were OK, ministers then passed round an "SOS" to be signed - an agreement calling for carbon emission cuts.
"We must unite in a global effort to halt further temperature rises," the message reads.
"Climate change is happening and it threatens the rights and security of everyone on Earth."
Meanwhile, a handful of journalists kitted out in snorkel gear and swimming around on the surface tried to get a glimpse of the action below.
Emerging out of the water, a dripping President Nasheed removed his mask to answer questions from reporters and photographers crowded around on the shore.
"We are trying to send a message to the world about what is happening and what would happen to the Maldives if climate change isn't checked," he said, bobbing around in the water with his team of ministers.
"If the Maldives is not saved, today we do not feel there is much chance for the rest of the world."
Curry and coconuts
After the dive, the president told the BBC he had seen a stingray swim nearby during the meeting.
"There was a sergeant fish that was particularly interested in what was going on," he said during a typically Maldivian lunch of fish curry and coconut juice.
"I've never been worried about reef sharks and I've been diving for a long time," the 42-year-old added.
He says other Maldivians had heard about the event and wanted to get involved in some way.
On the island of Kuda Huvadhoo, some islanders reportedly created a sealed box and put their TV in it so they could watch the footage of the meeting underwater.
"They told me, 'if the president is under water, then they want to be too'," Mr Nasheed said.
But he was keen to push the need for action.
The 1192-island chain is at severe threat from rising sea levels, with 80% of its islands less than a metre above sea level.
"What do we hope to achieve? We hope not to die. I hope I can live in the Maldives and raise my grandchildren here," says Mr Nasheed.
