The decoration of the Christmas tree is not a Greek habit. It is said that the first Christmas tree in Greece was decorated by the Bavarian king Otto in 1833. In Greece, according to the tradition, we decorate a boat, mainly on the islands. The boat symbolizes the maritime identity of the country. Greeks, a seafaring nation, of course combined the celebration of Christmas with the sea. The decoration of the ship was also a kind of honor and welcome to the sailors returning home to celebrate Christmas with their families.

Children used to make their own boat, using wood and paper and then decorate them with colorful fabrics, cotton and twigs. On Christmas Eve, many groups of children were singing carols from house to house, having with them the handmade boats and filling them with the treats they received.

Unfortunately, this custom disappeared over the years and the tree replaced it. However, in recent years, we see that the boat becomes popular again for a Christmas decoration, on the islands as well as in Athens.

Source: https://www.omilo.com/el/greek-traditional-christmas-boat/