Underwater 3D triangular range-intensity correlation imaging(RICI) is a novel scannerless 3D imaging technique beyond underwater visibility range, and can fill the current gap between short-range high-resolution conventional video cameras without 3D information and long-range low-resolution sonar systems. The development of 3D RICI was reviewed, and the introduction of 3D triangular RICI in the Institute of Semiconductors, CAS was focused. A 3D triangular RICI with multi-pulse time delay integration method was proposed, and the typical time parameters in the method were given. The prototype 3D range-gated imaging systems of Lvtong, Fengyan, Longjing were established, and can realize 3D imaging with 1 360 pixel×1 024 pixel beyond the visibility range of 4.8 AL. The systems have been used in fishnet detection, marine in situ detection, underwater target detection and recognition.