Can someone tell me if we HAVE to get off the ship at a certain time if we want to go to the ports of call and do we have to wait until a certain time to get back on the boat? I'm just wondering if decide we would like to board the ship earlier than the boarding time, can we? Like if we're tired of walking around the beach, or want to enjoy the quieter times on the boat while most cruisers are off it. Since this is my first cruise, I'm not sure how this all works. Is it an "open door" policy where you can get off and on throughout the port day?