I, too, carry a large purse on the plane, empty it and toss it on a closet shelf. Valuables go into the safe, take a card like a Safeway card or the like to use to lock the safe. If anyone gets a hold of it, you aren't out much. Carry only the sail and sign card on board, in a small hip pack. I have a larger hip pack (holds my camera, etc.) which goes ashore if we aren't doing anything wet. A beach bag will go if we needs a change of clothes, etc.
Hope this helps.