While many of his fellow player spent the off-season on the beach, the Grizzlies center decided he could not watch a humanitarian crisis from the sidelines

Marc Gasol will never forget the terrified look on the face of Josefa, the Cameroonian woman left clinging to a piece of wood for 48 hours in the Mediterranean. Josefa was the survivor of a shipwreck about 90 miles off the Libyan coast last Sunday. Rescuers recovered two bodies in the water alongside her, including that of a toddler.

“There were pieces of wood and clothes floating in the water,” Gasol told the Guardian. “Then there was that woman, with her elbows resting on a wooden beam. Her eyes were lost in the void. She was weak and in shock. She had been clinging to that piece of wood with her last bit of strength and had remained that way for 48 hours. I thought of this woman, of her strength. And I felt anger.”

For the last week Gasol, who plays for the NBA’s Memphis Grizzlies, has been volunteering on board the Open Arms Proactiva, the ship that rescued Josefa and collected the bodies of her fellow travelers. Gasol has actively participated in rescue operations: he threw himself into the sea to try to recover the bodies of the migrants and helped bring Josefa on board.

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“She would have died, after a few minutes, if we had not intervened,” Gasol said by phone from the rescue ship as it sailed for Mallorca. This summer Gasol who, along with his brother Pau, is one of Spain’s most famous athletes, has immersed himself in charity work with NGO Proactiva Open Arms. While many of his fellow NBA stars have spent the summer on the beach, Gasol has chosen to work with migrants in the Mediterranean. Initially the 7ft 1in All-Star chose not to publicize the decision. But then, at the sight of the bodies in the waves and Josefa’s terrified face – and with photos of her rescue having circulated on social media – Gasol stopped holding back. He posted a tweet in which he expressed “anger and frustration” at what he had seen.

“It was too important not to tell the world ... I could no longer remain silent,” he said. According to the UN, 1,443 people have died or gone missing attempting to cross the Mediterranean so far this year.

Facebook Twitter Pinterest Marc Gasol (left) and his brother Pau playing against each other during a friendly in Spain. They are two of the country’s most famous athletes. Photograph: Robin Townsend/EPA

Italy’s new populist government has vowed to halt the influx of refugees, and has given aid to Libyan authorities to stop dinghies from making the journey across the Mediterranean. Human rights activists say people being returned to Libya are at risk of beatings and rape. “I do not understand why [the Italian government] is preventing ships like Proactiva from bringing migrants safely to their ports,” said Gasol. “These people save lives every day.”

Marc and Pau help run their own charity, the Gasol Foundation, which funds projects for the world’s poorest children but this summer Marc took more direct action and sailed with Open Arms. After three days at sea, the ship found the wreck that left Josefa stranded in open waters.

Gasol did not hold back his emotions when he talked of the recovery of the drowned toddler. “I will never forget that child,” said the 33-year-old. “I am a father. I have children. And I imagine the pain of a father who is forced to face a journey like this where one risks everything, one risks one’s own life, to reach a country where one can live in peace and with dignity.”

Riccardo Gatti, the head of the Open Arms mission, said he is happy to have Gasol’s help. “It’s great to have Marc on board, we always need help here. Everybody is welcome on our boat. We always said that. It is important that people like Marc spread the word about what’s going on here.”

Gasol will soon return to the United States to prepare for the new season with the Grizzlies, but he will not forget his time on the Mediterranean. “I cannot understand how anyone can turn away from these people who are dying at sea,” he said. “How can we pretend it isn’t happening?Before being an athlete, I’m a person, a human being, like the ones Open Arms are saving every day. We must work so that these tragedies never happen again. We are all responsible.”