Abstract: Aiming to address the drawbacks of existing branched cables for underwater and dynamic applications, including excessive bulk, high weight, inadequate waterproofing performance, and inconvenient installation of the branch structure, this paper presents a novel compact and lightweight multi-layer transverse watertight branched cable, along with its corresponding manufacturing method. By leveraging high-strength silver-plated copper alloy conductors maturely applied in the aerospace industry, the proposed cable innovatively adopts a polytetrafluoroethylene (PTFE) wrapping insulation process to achieve extreme miniaturization and weight reduction. Furthermore, a unique multi-layer transversely arranged branch configuration and an elliptical cylindrical vulcanization sealing structure are specially designed. Experimental results indicate that the proposed cable maintains zero water leakage under a transverse water pressure of 1.5 MPa, and delivers outstanding mechanical performance: it withstands more than 10 000 cyclic bending tests and more than 10,000 cyclic flexion tests, while meeting the tensile strength requirements of ≥ 200 N for the main cable and ≥ 50 N for the branch cables. These properties enable the cable to satisfy the service requirements under repeated bending, flexing and tensile loads induced by high-frequency motion in underwater environments. The developed technology provides a high-performance and high-reliability cable solution for underwater equipment, marine vessels and offshore engineering applications.