Immersion ultrasonic NDE is performed within cavities of inanimate objects, having downwardly directed openings, such as for in situ inspection of steam inlet sleeves and steam inlet necks within steam turbine housings. A shaft assembly has one or more single angle or phased array ultrasonic probes that are affixed on an upstream or distal end. An inflatable bladder is affixed to the shaft on a proximal end of the shaft assembly downstream the ultrasonic probe(s). The shaft is inserted into the cavity opening, and the bladder is inflated to form a fluid tight seal against the cavity. Immersion fluid is introduced upstream the bladder in the volume occupied by the probes. Immersion ultrasonic inspection of the object is then performed.