I've taken 1 hr, 2.5 hr, and also renting a boat. Used to go there every year.
Based on my experience and personal opinion, 1 hr is just right time for a cruise tour. Among all choices, renting a boat is so much fun. There are several public islands you can get on as well. Check on those marinas for details, used to be $40 for half day including a full tank gas.