Abstract: Typically, unattended underwater devices are deployed for extended periods. As underwater energy supplies are limited, it is crucial to reduce energy consumption to prolong operational time. To address incorrect wake-ups caused by double-selective and noisy underwater channels, an underwater acoustic wake-up system devices based on time-frequency detection is designed using the GD32F4xx. The system can collect and process signals in real-time, achieving independent wake-ups for different devices through distinct address codes. Sea trial results with a 1 km range and an average signal-to-noise ratio of 30 dB show that the average wake-up success rate of this system is 95.2%, with an incorrect wake-up rate of 0. Additionally, a 60% wake-up success rate is achieved even at a −6 dB signal-to-noise ratio.