Most Australians will have a family meal on Christmas day and exchange presents. It probably won't be a barbecue, and it is most unlikely to be on the beach. Instead it will be somewhere cool and shaded, indoors with the airconditioning on possibly, but perhaps outside in the garden under a shade sail.
A decorated tree in Manly, a Sydney beach suburb.
Seafoods, salads and sparkling wines are likely to feature strongly on the menu, especially if you are near the coast with access to good prawns and oysters. If your family is of British ancestry, as mine is, then the meal is likely to contain some remarkably similar elements to that which your cousins in the Old Country are enjoying -- a large roast of some sort and a steamed Christmas pud.
wherever you are and whatever your Chistmas tradition is.