Olympic champions Serbia made it two victories out of two as European qualification matches in the men's International Swimming Federation (FINA) Water Polo World League continued.
The Rio 2016 gold medallists proved to be too strong for hosts Germany in Berlin and came away with a 15-9 victory.
It means they top Group A after their opening success against Romania last month.
In the other game in the group, Romania recovered from their loss by beating Slovakia 12-10 in home water in Izvorani.
Slovakia had earlier begun with a win over the Germans.
In Group B, London 2012 Olympic champions Croatia also made it two victories from two as they beat winless hosts France 14-9 in Montpellier.
Greece hosted The Netherlands in Pireaus and claimed a first victory, denying the Dutch a second win in the process with a 9-8 success.
In Group C, a three-team group, Italy claimed an away win by beating Russia 10-7 in Ruza.
It means both countries boast a victory each, with Georgia bottom of the group.
Only the trio of group winners will make it through to next year's Super Final, which has yet to be allocated a host nation or dates.
They will be joined at the Super Final by the host nation, as well as four non-European teams who progress from an Intercontinental Tournament.
The next qualifiers will take place on January 10, with the countries playing each other on a home-and-away basis.