A video grab showing a spectacular waterspout off the coast of Bastia, on the French island of Corsica, yesterday as the island was ravaged by storms and rain. In some places, the downpour reached 60mm in less than an hour. Waterspouts typically form beneath cumulus or cumulonimbus clouds over warm coastal waters just before showers begin. The "funnel" is formed by water droplets in a rotating vortex of air. The lifespan of a waterspout can vary from a few minutes to half an hour.