On the southwest end of Skiathos island lies a large sandy bay called Koukounaries. There is a small harbour tucked away in the eastern corner. You will find good shelter from wind and swell here, with great holding for the anchor. There is a large visible hotel at the eastern side of the bay. The best places for anchoring is far east or west - find a sandy area and avoid any seaweed.
Lockie (Sporades Engineer 2013) says: "This beach was voted 10th in the world. The sand is golden and the water clear. There are a number of companies that offer watersports for a reasonable price. Mooring is free-swinging so the dinghy is required to get to shore, but the main town features a number of great tavernas and a stunning steak house so it is worth the trip..."
Koukounaries has a forest reserve behind the beach and beyond that there is a lake/lagoon connected to the sea by a river that emerges at the little harbour, which you can explore in your dinghy. During July and August, the bay is a hub for water skiers and all sorts of other water activities, but the nights are usually peaceful.
The small harbour is too small for a whole flotilla on the inside, but an imaginative flotilla skipper might get some of the boats tied up somehow or other. The most common option is to anchor one hundred metres or so from the small harbour out in the bay opposite the sandy beach that extends along to the west.
Yellow buoys mark the area in the middle of the bay that is prohibited for anchoring as it is a waterskiing lane in July and August. Ashore it is a fifteen minute walk to supermarkets and tavernas. This option of course will require your dinghy to get ashore.