The lovers seem to be in a nice room overlooking the straight that spans England and France. They can perhaps see the moon sparkling on the waves of the water. They may get lost in the cadence of the ebb and flow of the tide coming and going. Since the poem wanders through the years of rich history and faith that this straight has endured, the speaker seems to realize the fleeting ability of time. Therefore, in the end he tries to capitalize on this moment as demonstrated in the words
Ah, love, let us be true
To one another!
The speaker notes that nothing else in the world fulfills like loving each other. Their relationship is particularly difficult to see or visualize, but if nothing else, these words reveal a longing for intimacy and companionship. The speaker recongizes futility in the world just after the above words making a grave comparison. To me, this is the image of a man ready to extend more love to his lover in light of the fleeting nature of life.