The zookeepers had barely opened the door from her enclosure, when the four-month-old bounded out into the open with her mother Valeska by her side.
After tumbling through the artificial mountainous landscape, Lili leapt straight into the three-meter-deep pool.
“My heart almost stood still,” zookeeper Frank Schlepps said of the moment.
But the weather didn't keep its side of the bargain on the morning of the grand debut, with drizzly rain putting off all but a handful of animal enthusiasts.
“She's already eating minced meat and she loves chewing on bones and branches,” Joachim Schöne, another Bremerhaven zookeeper, said of the cub, who weighs a healthy 25 kilograms.
“Every day she is putting on about 300 grams in weight," he added.
For another year she will also bulk up on the fat-rich milk from her mother's teat.
Lili's healthy early childhood is in stark contrast to that of Knut, the Berlin polar bear who won the hearts of children the world over with his brave struggle against adversity.
After being rejected by his mother after his birth in 2006, Knut was raised by zookeepers.
When he was first introduced to the public at the age of 15 weeks, he only weighed nine kilograms. But a cult of 'Knutmania' quickly emerged around him and in 2007 the Berlin Zoo pulled in its highest earnings in its 163-year history.
But animal rights activists and keepers from other zoos said their Berlin colleagues should have had the courage to let Knut die, arguing that it was cruel for him to be raised without a mother.
Local school children responded by protesting outside with placards reading "Knut must Live" and "We Love Knut".
In 2011, Knut collapsed and died in front of visitors. A neuroscientist later discovered that he suffered from anti-NMDA receptor encephalitis - a disease in which antibodies attack healthy nerve cells in the brain.