Then he saw a man flailing in the water.
"We hurried and pulled the man out," Grbic recalls. "I remember telling him: Such a glorious day and you want to kill yourself!"
It was the first time Grbic saved a life. From that day 15 years ago, his own life would never be the same. The bright-eyed, tattooed restaurant owner from a shabby industrial zone on the outskirts of Belgrade has rescued 25 people who tried to kill themselves by jumping off the tall bridge over the Danube.
Always on alert in his little wooden motor boat, the burly 51-year-old has pulled people out of the river's muddy waters without asking for anything in return.
"I couldn't turn my back on them," Grbic said. "They are desperate people."
Grbic has been dubbed the "Superman of the Danube" by his admirers and awarded a hero's plaque by Belgrade city authorities. But even "Superman" can't save everybody who jumps off the 18-meter- (60-foot-) high bridge: At least as many as he had saved have killed themselves at the spot since Grbic's first rescue.
"When I hear that someone has jumped and I wasn't there I really feel bad," he said. "My eyes are always on the bridge.
The Pancevo bridge became a favored suicide spot because it is Belgrade's only bridge over the Danube, which is bigger and colder and has stronger underwater currents than the city's other river, the Sava.
The first person Grbic pulled out of the Danube turned out to be a mental patient. Grbic took him ashore, gave him dry clothes, hot tea and cigarettes. Later, an ambulance came and took the man away.
"That was it," Grbic says. "He didn't speak, they never do."
Over the years, Grbic has rescued men and women of all ages and social backgrounds. Grbic remembers them all, but "they never return or call, they hardly ever say thank you."
Goran Penev, a researcher with Serbia's Institute of Social Sciences, said Serbia's suicide rate is at the upper side of the European average. Penev noted there was a sharp rise in the early 1990s, at the beginning of the wars in the former Yugoslavia, but the situation has been relatively stable ever since. In 2011, nearly 1,300 people in Serbia—a country of 7 million people—took their lives.
Grbic has found that some of the people he rescued had cancer or other terminal illnesses, while others cited poverty or unrequited love.
All, he said, felt lonely.
"It is a cry for help," he said. "They often do it in daytime so they would be seen. They want attention, love."
Only a couple of weeks ago, a 22-year-old girl threw herself off the bridge near Grbic's restaurant. He was there to pick her up and ask: "Why did you do it?"
"For my boyfriend," she replied. "Do you think he would do it for you?" he asked in return.
Grbic said the girl was conscious and clear-minded when he plucked her out of the water. In winter, however, it is a question of minutes before people will lose consciousness in the freezing Danube and drown.
On one of those days, in mid-January about seven years ago, Grbic was just preparing to turn his boat to shore and go home—when he heard a scream.
An 18-year-old woman going through a mental crisis had burst out of her parents' car at the bridge, taken off her jacket and jumped, shouting: "Goodbye mom!"
Grbic said something had made him stick around: "It was a very windy day, a few minutes later and I would have gone."
The girl, Grbic said, is the only one who has stayed in touch.
Every January she comes to his fish restaurant to celebrate her "second birthday." She is married now and has a child. Grbic was invited to the wedding reception.
"My heart leaps every time I see her," he said.
Grbic has little or no information about what happened to the others he saved. It would be nice, he says, if they came to tell him how they were over a brandy at his restaurant.
"I gave them a second chance and it was up to them to use it well."