Abstract In this paper, the underwater applications of micro‐LED (light‐emitting diode) in light emission, optical detection, and solar cell are demonstrated. Based on a high‐bandwidth and low‐power micro‐LED array, duplex underwater wireless optical communication (UWOC) and underwater charging are realized. Using the non‐return‐to‐zero on‐off‐keying modulation scheme, the maximum modulation bandwidth and data rate of a micro‐LED transmitter in the 2.3 m duplex UWOC system are 251.3 MHz and 660 Mbps, respectively. In addition, the micro‐LED‐based photodetector can achieve maximum data rates of 52.5 and 60 Mbps at 0 and −5 V in the same UWOC system, respectively. Furthermore, while achieving the communication function, the micro‐LED is used to realize the collection of external light energy, which is successfully employed to drive a 660 nm laser diode, proving the photovoltaic power generation of micro‐LED. This experiment has made a breakthrough in the duplex UWOC system based on an InGaN micro‐LED array, and verifies significant potential of micro‐LED application in the field of duplex UWOC and underwater charging.