 The metal disc from the satellite is not destroyed, instead making it through the Earth's atmosphere and landing at the lagoon, eventually being found by Gilligan.The Professor realizes that a unique alloy in the disc can be used to make a barometer enabling him to predict the weather for the first time since their radio finally gave out.While using the new barometer, the Professor deduces that they are going to be hit by a tsunami of such magnitude that it will destroy the island.