A system for non-destructively inspecting tubes is provided. The system may include a tank filled with a fluid, e.g., water. The tank may define an axial passage within it for tube insertion, and the tank may include an opening to the axial passage. A transducer probe may be disposed inside the tank and oriented toward the opening to the axial passage. The system may also include a movable seal including a chamber, configured to move axially in the axial passage, and a membrane positioned in the opening of the tank. During inspection, an acoustic pathway may be provided between the transducer probe and the tube, the pathway including fluid in the tank, the membrane, and fluid in the chamber.