High-capacity, long-distance underwater optical communication enables a global scale optical network covering orbit, land, and water. Underwater communication using photons as carriers has a high channel capacity; however, the light scattering and absorption of water lead to an inevitable huge channel loss, setting an insurmountable transmission distance for existing underwater optical communication technologies. Here, we experimentally demonstrate the photon-inter-correlation optical communication (PICOC) in air–water scenarios. We retrieve additional internal correlation resources from the sparse single-photon stream with high fidelity. We successfully realize the 105-m-long underwater optical communication against a total loss up to 120.1 dB using only a microwatt laser. The demonstrated underwater light attenuation is equivalent to the loss of 883-m-long Jerlov type I water, encouraging the practical air–water optical communication to connect deeper underwater worlds.