プログレッシブ和英中辞典(第4版)の解説
かんまん【干満】
high and low tide; ebb and flow
この辺の海岸は潮の干満の差が大きい
There is 「a great range of tides [a great difference between the tidemarks] along this part of the coast.
潮の干満のように人生には起伏がある
Just as the tide rises and falls, so life too has its ups and downs.