Possession sound, a branch of Puget Sound, is ideal for boating. The waves are generally small (though not always) and it is often calm enough for small boats, such as rowboats and canoes. The most common weather pattern in the summer is relatively calm in the morning, moderate winds during the afternoon, dropping off near sunset. You can launch car top boats from the beach, or use one of the public boat launches on the link below.
Click here for Puget Sound Marine Weather.
Click here for Whidbey Island Boat Launches and here for a more detailed map.