Sailing dinghies, jet-skiers and even paddle-boarders are potentially putting their lives at risk by going too close to a sunken Second World War munitions ship.

The SS Richard Montgomery was wrecked on the Nore Sandbank in the Thames Estuary off Sheerness in August 1944 while carrying 1,400 tonnes of explosives.

The bomb-laden ‘Doomsday’ wreck lies in only 15m of water and the explosives are still on board.

People might assume that after almost 80 years the chances of a detonation are remote, but that is not necessarily so, as the wreck itself is becoming destabilised.

For safety’s sake, there is an 500m exclusion zone around the vessel which is marked by four yellow light buoys and 12 orange buoys.

No-one is allowed inside the zone except government-authorised survey vessels who check on the wreck once a year.

The Richard Montgomery’s masts project above the water level and in recent years the government has determined these will have to be removed, as the strain they place on the wreck could aggravate the deterioration of the hull. So far that work has not been carried out.

There have been various estimates over the years of the damage that would be caused to Sheerness, if the Montgomery were to explode, with one study predicting the town would be swamped by a five-metre high tidal wave – although other reports have been less apocalyptic.

The exclusion zone is monitored visually and by radar by the Maritime and Coastguard Agency.

Radio enthusiast Richard Hurley of Ypres Drive, Sittingbourne, said he was at Minster Beach on Sunday.

He said: “I was listening to my marine radio while watching the sail boats.

“It soon became apparent how many mariners and water-sport enthusiasts were breaching the exclusion zone around the Montgomery masts.

“I personally saw the exclusion zone breached at least 12 times in a two-hour period between 1pm and 3pm.”

“I also heard the portmaster at Medway VTS at Garrison Point call out to general traffic in the estuary to be on the lookout for mariners who were breaching the zone and to report these instances to the coastguard.

“The vessel Joseph Marley, a small passenger boat, reported several breaches of the zone while it traversed the estuary and due to the number of reports being made, and in the absence of the coastguard, the portmaster then advised all vessels to phone 999 or use the emergency Channel 16 to report these breaches directly to the coastguard's control room.

“I personally saw jet skis, water paddles, sail boats, and clippers.

“It's becoming a very dangerous affair indeed.”

It is also illegal, with those ignoring the rules risking a hefty fine or imprisonment.

Our priority will always be to ensure the safety of the public and reduce any risk posed by the SS Richard Montgomery

Essential preparatory work to remove the ship’s masts was undertaken in autumn of last year including highly detailed surveys of the wider wreck site and seabed.

These studies identified several potential challenges to successful completion and as a result, the Department for Transport (DfT) says it has been necessary to review the project to determine “alternative solutions” for their safe and effective removal.

Despite this DfT says it remains committed to the removal of the SS Richard Montgomery’s masts and is working hard to progress this project.

It says the work completed so far has been extremely valuable in further enhancing its understanding and providing additional information which will inform the future management of the site.

A Department for Transport spokesperson said: “Our priority will always be to ensure the safety of the public and reduce any risk posed by the SS Richard Montgomery.

“We commissioned experts to carry out vital surveying work to the wreckage.

“Based on the latest findings of the report, we are revising our initial timeframe and are updating our strategy to remove the ship’s masts in the safest manner possible.”