Is this Channel Islands hike doable in one day?

I'm trying to decide if I can squeeze a Channel Islands trip into one day or if I should camp overnight. I've done a hike of similar distance and elevation (which was also partially in ankle-deep snow) in just over six hours. If I only take the ferry for the day, it would leave at 8:00 am and pick up at 4:00. Is this a reasonable hike to try to fit within the ferry schedule?