The environmentalist swam with brown and tiger sharks in a tank at the London Aquarium to highlight a global survey which records widespread damage across the world to the living eco-systems.
Over 200 teams of divers in more than 40 countries took part in the survey to obtain the first-ever snapshot of the state of the world's reefs, studying environmentally fragile areas including Malaysia, the Red Sea and the Caribbean.
The findings highlight an alarming range of threats, including anchor damage, overfishing of commercial species, pollution and damaging dynamite fishing.
It is feared that 10 per cent of the world's reefs have already been degraded beyond recovery and that another 30 per cent are rapidly heading that way. Only 1 per cent have any official protection.
"If you need proof of the plunder of our coral reefs and the need for an International Year of the Reef, ask yourselves where all the sharks have gone," Professor Bellamy said.
"More and more shark species are appearing in the red data book of endangered species, a sure sign that the natural balance of reefs is in danger.
"Once these large predators have gone to fuel the demand for shark-fin soup and shark steaks, populations of other fish and invertebrates explode, speeding the destruction of coral reefs.
"Of the 109 countries with reefs, over 85 per cent have suffered some kind of damage from our careless actions and in some cases the environmental and economic consequences have been disastrous.
"This destruction simply has to stop, otherwise within 40 years over half our planet's coral reefs will have vanished."
Alastair Harborne, UK Reef Check Co-ordinator said: "Reef Check clearly shows that if nothing is done now to save these rainforests of the seas, we risk losing some of the most beautiful, diverse and important habitats on earth."