What metaphors are used in Fiddler Crab by Josephine Jacobsen?

In the poem, Fiddler Crab, the tide and the waves are metaphoric on several levels. First, time appears to happen in irregular intervals. The waves represent the strange, unpredictable moments in time. The tide, like minutes, hours, days, and weeks, can be predicted and plotted. The moments, however, remain an unpredictable. Time clearly passes from today to tomorrow, just as the tides shift from high to low, but from moment to moment the waves are like the mysterious instances that cause humans to feel a strange relationship to time and its passing. These mysterious instances happen in the present. The effects that follow are unpredictable.