I'm booked on a small (50 person) boat and we will be traveling between several islands during late April. I do not usually get seasick, but wondered how rough the seas might be since it's a relatively small boat.
It is impossible to answer this question, the sea can be calm and everything will be fine or there will be a stormy sea with 9Bf winds and your boat will not leave the dock.
They do have winds called Meltemis in the Aegean which caused a bit of havoc with our trip to Santorini a number of years ago in May. When those kick up, it’s possible you will be stuck in port. Nothing will be moving on land, sea or sky when that happens. If you are concerned about heavy seas but don’t normally get seasick, take some Bonine if there is a day where it’s possibly going to be rough. My husband never gets seasick and doesn’t take anything and only felt mildly queasy in 20 feet seas in Antarctica.