Greece began the defence of their International Swimming Federation World Men's Junior Water Polo Championships title, with victory over Australia in Kuwait City.
The Greeks recorded a comfortable 16-9 win to get their Group D campaign off to the best possible start at the Al-Nasar Sport Club in Kuwait City.
In the other match in the group, New Zealand thrashed Uzbekistan 22-6.
Last year's runners-up Croatia also began with a win as they defeated South Africa 16-5 in Group A.
Japan edged out China 12-9 in the second contest in the group on the opening day.
In Group B, Canada beat Egypt 12-8 and Spain ousted Hungary 9-7.
Hosts Kuwait lost their first game, going down 15-7 to Iran in Group C.
Italy earned an impressive 18-11 win over the United States in the other encounter in the group.
Action continues tomorrow.