10 mins on the local bus (every 15 mins) at bus stop 15.
Skiathos is only 7miles long and Skiathos Diamond apartments are in Kolios about halfway
I would say about a 20 to 25 minute walk. some of it is along a very busy road though so I recommend crossing the road, turning right instead of left the walk down alley at side of shop, THEN turn left. this avoids the majority of the road
Get an answer from Skiathos Diamond Apartments staff and past guests.