homarid enters the battlefield with a tide counter on it.
at the beginning of your upkeep, put a tide counter on homarid.
as long as there is exactly one tide counter on homarid, it gets -1/-1.
as long as there are exactly three tide counters on homarid, it gets +1/+1.
whenever there are four tide counters on homarid, remove all tide counters from it.