Ecos do Mar follows Aurora and Armindo, an elderly couple who walk into the ocean to end their lives, only to miraculously wash ashore fully rejuvenated into their youth. Stranded with young bodies but twentieth-century minds, they must navigate the overwhelming complexities of modern culture, technology, and newfound temptations that strain their decades-old marriage. As external suspicions mount and the mystery of their transformation deepens, the couple is forced to confront whether to embrace this second chance or return to the sea to face their original destiny.