Complex sentence: The Royal Navy Bomb Disposal Unit unsuccessfully attempted to demolish the wreck in 2010, following which it was then marked with a buoy, and in March 2011 work started to demolish the remainder of it using saws.
Split into simpler sentences: The Royal Navy Bomb Disposal Unit attempted to demolish the wreck in 2010, but failed to do so. It was then marked with a buoy, and in March 2011 work started to demolish the remainder of it using saws.