As the owner/operator of the boat, understand you are likely going to be held responsible for any injury or damage caused by your boat, whether it is attended or not. Why take the added risk of leaving your boat unattended? I have been a boat owner for 39 years, have used them for family recreation with some diving, and would never consider leaving my boat unattended while playing in the water or diving. If you can't find a fellow diver or friend to go out with you, then you need more friends.