A nozzle for delivering a laser beam to a workpiece under water includes a hollow plenum having an axially spaced apart inlet and outlet, with a gas port disposed therebetween. The laser beam is delivered through the inlet and outlet toward a localized melting zone on the workpiece. A pressurized cover gas is delivered into the gas port for discharge through the outlet to cover the melting zone. The outlet is sized to discharge the gas as a jet for opposing pressure of the water to locally exclude the water at the melting zone.