How is a water spout measured?

If a waterspout makes landfall and causes damage then it will likely be recorded as a tornado and given a rating on the Enhanced Fujita scale based on the severity of the damage it inflicts. If the waterspout stays on the water it usually will not be recorded as a tornado and so will not receive any rating. Occasionally, though, such a waterspout, having done no damage, will be recorded as an EF0 tornado.