Immersion probes are typically used in semi-automatic or automated flaw detection systems. The workpiece and probe are immersed in water, maintaining a certain distance between the probe and the workpiece's inspection surface due to "water delay." The probe does not directly contact the workpiece, thus enabling flaw detection of irregularly shaped, geometrically complex, or rough-surfaced workpieces.

When the probe's emitted sound beam axis is perpendicular to the inspection surface, a longitudinal wave straight beam scans the workpiece. Adjusting the probe's sound beam axis to a specific angle with the inspection surface causes the sound beam to refract at the interface between the water and the workpiece, generating a tilted transverse wave sound beam within the workpiece for further inspection.

By machining the acrylic glass or cured epoxy resin in front of the probe wafer into a certain curvature (spherical or cylindrical surface), point-focused or line-focused immersion probes can be obtained.

The probe has a flat surface and is not focused. It comes with a probe cable and a BNC plug for direct connection to the instrument. The focal length of the probe in water is equal to the near-field distance N=D2/(4λ), where D is the effective diameter of the crystal and λ is the wavelength of the sound beam in water.