I think as do some of the locals that the severe erosion of this section of the beach was due to the placement of many large stones in front of the Delphino Blue.
These stones distorted the water and tidal current during winter storms and 'back washed' the sand out to sea where it now sits in long ridges 30 meters out.
However this erosion is part of a larger scale shrinkage of the beach over the last few years which I think has been due to a succession of stormy winters in Corfu.
I have photos of the beach from my first visit in 2008 and it was massive, but when you check the weather records for Corfu between 2000 and 2008 you will find a long series of calm winters with few winter storms, however, winter 2009 was stormy and 2010 and 2011 even stormier as deep low pressure systems crossed Greece during the winter months. The recent winters 2012 to 2015 have seen further stormy winter spells although not as bad as those between 2009-2011.
We need a return of those calmer drier winters in Corfu to restore the beach and with high pressure now extended across the Eastern Mediterranean this winter could be the start of a beach revival.
Andy