The animation shows results from a recent GOTHIC simulation of a test performed in the Marviken experimental facility in 1976. The test includes venting of air, then steam, through vertical vent pipes submerged in a pool of water. The vented air forms large bubbles in the pool and lifts the pool surface. The steam venting that follows results in smaller bubbles that condense in the pool. This simulation validates GOTHIC's ability to predict vent clearing, pool swell and condensation heat and mass transfer in steam bubbles.