A laser shock peening apparatus is provided for use with a workpiece having a cavity. The apparatus includes a tubular body configured for insertion longitudinally inward of the cavity. The tubular body has a peripheral wall bounding a laser delivery channel, and has an aperture reaching outward from the laser delivery channel through the peripheral wall. An optical device is located in the laser delivery channel. The optical device is configured to direct a laser beam outward through the aperture. Additionally, the peripheral wall has internal surfaces defining a water delivery channel configured to convey a stream of overlay water to the aperture.