The interaction of continuous CO2laser radiation with water is described. Tightly focused radiation at powers of up to 120 W is used to generate and maintain a conical depression in the water surface similar to the keyhole created during laser penetration welding. The observed penetration depth of up to 7 mm is explained in terms of a hydrodynamic model and observations on the interaction induced liquid flows are described. The momentum reaction to the flow of steam up out of the keyhole generates a downward flow in the liquid around the keyhole with a velocity of ∼20 cm/s under the conditions of these experiments. The experiment has also been performed under variable gravity conditions provided by the NASA KC‐135 Microgravity Aircraft to observe effects associated with changes in hydrostatic pressure and buoyancy on the system.