A swirling eddy of warm water that has been lingering around Bermuda since July is causing tides to rise by up to 40 centimetres, leaving the Island vulnerable to more damage than normal if a hurricane strikes.

Yesterday tides were so high they came close to going over the bridge at Ordnance Island, St. George's, and were lapping close to diners in the Old Town's White Horse Restaurant.

A similar phenomenon happened two years ago but it is much worse now because the giant eddies of warm water are lingering longer, said Bermuda Biological Station for Research (BBSR) director Dr. Tony Knap yesterday.

He described the tidal rise as "huge" and said the Island could suffer severe damage if a hurricane struck while the water was so high.

The eddies, which form in the Sargasso Sea, can be 1,200 metres deep and up to 800 metres wide.

Because they are warm, they are causing the sea level to rise and for some reason are lingering around the Island longer than usual.

Dr. Knap said BBSR is studying when the tides last rose this high due to a lingering warm water eddy.

"This is cyclonic and it is warm.

"It is raising the mean sea level of the Island by 30-40 centimetres.

"That's huge," he told The Royal Gazette yesterday.

"These are eddies which change the tidal range.

"They lift the water up more and this still has an influence because it is warm.

"It is between 400 and 800 metres wide and that has expanded so it has elevated the mean tide level.

"The tides don't go down as low as normal and they go up higher and don't go down.

"This was over Bermuda and it is still hanging around.

"Sometimes you get eddies with cooler water that drop the water level.

"We have seen Shelly Bay almost empty out.

"Our dock is underwater by about six inches.

"This one is moving much slower than others that go past.

"Two years ago we had a similar one but not as long lasting."

When asked if there was a danger of flooding, he said: "I don't know, but friends of mine have property by the water and they are finding their lawns are getting wet.

"If we get hurricanes or something hitting an extremely high tide it is going to do a lot more damage than if it hit when tides are lower."