Survey vessel 'EGS Watchful' was filmed this afternoon (May 18) undertaking (what's likely to be the final) sonar survey of Thames shipwreck SS Richard Montgomery and the surrounding seabed ahead of work to cut the masts off expected to start in June.

The wrecked WWII American Liberty cargo vessel is located 1.5 miles north of Sheerness in Kent, UK and sank in 1944 with an estimated 1400 tonnes of explosives still onboard.

The survey vessel bounces sound waves off the sea bed using sonar technology, which a computer will reconstruct into a detailed 3D model showing the condition of the wreck and seabed.

The survey vessel has special permission to enter the buoyed no-entry 'exclusion zone' surrounding the shipwreck which is monitored 24/7 by Port of Sheerness on behalf of the UK Coastguard.