Halong Bay is a beautiful place near Hanoi. It has multiple series of rocks that jut out of the water. I stayed on a boat for two nights here. I swam and kayaked in the beautiful waters. Without much in the way of boat docks, they had a very interesting system of putting boats up next to each other where you walk from boat to boat to get to the dock. You had to be there to appreciate this! At times this was rather challenging.