Time‐average optical holographic interferometry techniques have been used to obtain measurements of an array of sonar transducer elements operating underwater in a 15‐m‐diam 30‐m‐deep tank. Holograms were made from outside the tank through a pair of portholes using an argon‐ion laser. Measurements were made to provide experimental verification of predicted acoustically induced mutual coupling effects. The quality of the hologram reconstructions was sufficient to resolve fringes spaced 1 mm apart from a viewing distance of 7.5 m.