Blue/green light-emitting diodes (LEDs) show great potential in medium/short distance underwater optical wireless communication (UOWC) while suffering limited bandwidth caused by a long radiative recombination carrier lifetime and large resistance-capacitance (RC) constant. We designed, fabricated, and packaged a 75-µm single-layer quantum dot (QD) blue micro-LED with a record high modulation bandwidth up to 1.03 GHz. The single-layer structure of QD reduces the carrier lifetime and RC delay. A data rate of 2 Gbps over a 3-m air-underwater channel using a non-return-to-zero on-off-keying modulation format with a low bit-error rate of 2.03×10-3 was achieved below the forward error correction limit, which is the highest data rate of micro-LED-based UOWC systems, to the best of our knowledge.