It seems like all of Europe is visiting the islands in July and August. This if fine if you enjoy the busy environment but for those who value their privacy and are looking for a more unique experience, these are definitely not the months.
The winds can be quite strong during mid summer - the 'Meltemi' is the NW wind which can blow for days and make your voyage quite unpleasant so we were lucky but in any event our skipper was quite experienced and had encountered heavy gales before so we felt reasonably safe. I'm not the best sea-farer as I suffer from motion sickness but after the initial day of hanging over the back of the boat, I soon got used to it and acquired my sea legs with only the odd day of sea swells putting me off balance again! Our route took us around Aegina, Poros, Hydra and Spetses. All beautiful islands, particularly Hydra. We would often find a secluded bay where we could spend the day and sometimes the night, hop in the tender and find a nice little taverna to have dinner.
The harbours can get quite crowded so you often have to 'park' in rows and step over other boats to get to the shore! You can replenish fuel, water and empty the waste tanks at these moorings then stock up on your supplies and explore the islands or just take a day out to laze on the beach and do nothing if you choose!
I'm now looking forward to some pre-Christmas sun in just a few weeks .. top up the tan and those vitamin D levels before we plunge into another predicted icy cold winter!