Champion spearfisher Kimi Werner was given an assignment in second grade: Write an essay describing three individuals—past or present—that you would most like to meet. For the young Kimi, the selections came easy: Abraham Lincoln, the Earl of Sandwich, and her long-lost brother.

Growing up in rural Maui, Kimi knew she had an older brother somewhere out in the world. Her mother, June, had given birth as a teenager, giving her son up for adoption in the earnest hope that he would have a better life than what she was equipped to give him at that time. Though the adoption was closed, June had always been open about her decision with her daughters, Kimi and Christy, who were both born more than a decade later.

For Kimi, 37, her unknown sibling was a source of marvel and mystery. Throughout her childhood, she imagined her brother’s parallel life—his name, his appearance, his whereabouts—painting a rich narrative with a child’s fanciful wonder. But as years passed with no word from her brother, Kimi’s tenderly wrought dream began to fade. By adulthood, and well on her way as a rising star in the diving world, she came to terms with the likelihood of never knowing her sibling.

Then, when Kimi was in her 20s and living on O‘ahu, her brother initiated contact with her mother. His existence was no longer a fantasy. Moreover, he had a name: Randy Kosaki.

It had taken nearly 40 years for June to learn that her fervent wish for her son’s flourishing had indeed come true. “Money couldn’t have bought better parents,” Randy, 54, says of Richard and Mildred Kosaki, the couple who adopted him at birth. Randy knew of his adoption, but the details had been scant. “All I knew was that [my mother] had been very young and that I was part Hawaiian,” he says. “That was it.” Randy was raised in the Honolulu neighborhood of Mānoa, an only child in a loving and supportive household. “I was a geeky science nerd, and my parents were academics, both university people,” Randy says. “They encouraged whatever interests I had.” For Randy, such interests usually involved the ocean. One of his earliest memories includes being towed along on a surfboard while his father snorkeled. Soon, Randy was in the water, too. From middle school onward, Randy loved all things fish: diving for them, photographing them, cooking them, studying them. “It kind of became a hobby that got out of control,” Randy says. Naturally, he merged his passion with his profession, becoming a coral reef ecologist. Today, he serves as the deputy superintendent for the National Oceanic and Atmospheric Administration’s Papahānaumokuākea Marine National Monument, where he coordinates research and field operations.

With her brother’s name now known and their reunion imminent, Kimi recalls mining the internet for everything she could find on Randy. Each article and scientific research paper revealed a trove of information, a precious window into his life and personality. She favored interviews where Randy was quoted. “I felt like I was hearing his voice,” Kimi says. It was sweet compensation after so many years of silence. One article describing an ocean expedition during which Randy and his team had discovered new species of fish elicited a shriek of delight. In it, Randy explained that his favorite part of the research usually came afterward, when he finally heaved off the 150 pounds of cumbersome equipment and could free dive. “I remember thinking, ‘Oh my God! He totally is my brother!’” Kimi says.

Like Randy, Kimi had heeded the ocean’s ineluctable draw, her life’s path becoming a magical interplay of purpose, passion, and profession. Forgoing a conventional office job, Kimi focused on what she loved best: being out in the water. Today, she partners with National Geographic Society (she is a frequent host of adventure television show Nat Geo People) and companies like Patagonia, with whom she travels the globe, sharing her love of sustainable hunting and harvesting while exploring stories of cultures and people of the world. The discovery of her sibling’s twin passion for diving made wonderful, if not obvious sense. Ocean adventuring was in their blood.

Randy explains that it was the birth of his son Reece in 2004 that motivated him to seek out his own biological family. Though he had only ever felt compassionate toward his birth mother, Randy worried how accessing his birth records might disrupt her life. It was a fragile situation in which all parties were vulnerable. As fate would have it, Randy met his newfound sisters first.

“I was probably the most nervous I had ever been in my life,” Randy recalls as he drove to Kimi’s Kailua apartment for dinner. She prepared a fish she had caught while diving earlier that day. Sitting together to eat, the trio began the tender process of transforming from strangers to siblings. Christy and Randy bonded over their shared desire to nurture people. (Christy is a social worker; Randy mentors students in ocean science programs.) With Kimi, the ocean became the bridge. She marveled at the incredible similarity between their lives. As the siblings swapped fishing tales early into the morning, any residual anxiety melted away. “Our conversations made me feel like we had grown up together,” Kimi says. “Our hearts spoke the same language.”