cast tidal influence 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 tide counters on tidal influence, remove all tide counters from it.
