Tidal Influence [FEM-28]

Cast this spell only if no permanents named Tidal Influence are on the battlefield. Tidal Influence enters the battlefield with a tide counter on it. At the beginning of your upkeep, put a tide counter on Tidal Influence. As long as there is exactly one tide counter on Tidal Influence, all blue creatures get -2/-0. As long as there are exactly three tide counters on Tidal Influence, all blue creatures get +2/+0. Whenever there are four or more tide counters on Tidal Influence, remove all tide counters from it.