I'm searching for free data like Europe's coastline and Mediterranean island's names etc. but with good precision. I found some shp file from this site http://www.naturalearthdata.com/downloads/ but the data it was too generalized and the scale small. Free data usually is without any warranty about their accuracy. I need it for non commercial use.
OpenStreeMap uses Prototype_Global_Shoreline (PGS)
The data has been improved by users so the more accurate source is direct from OSM.
Errors still exist - a map showing these errors is available: http://wightpaths.co.uk/coast/
Here you have a very good shapefile for oceans and seas. You don't have island's names, but it has a very good precision.
I suggest you to download the non-simplified version, that has much more accuracy and complexity.