The first six lines of the poem evoke a mood of peace, quiet, contemplation, and tranquility. The first line creates an image of a calm sea at night. Mention of the moon in the second line enhances the picture of a calm sea under moonlight. Then in the third line the reader catches a glimpse of a far-away light, perhaps of a lighthouse, on the other side of the English Channel. The description of the cliffs of England standing vast creates a feeling of security against the elements, and "sweet is the night air" creates a feeling of warmth and of summer, since the speaker can stand at the open window at night by the sea. Just single words in the six lines help to set the mood. The significant words are: calm, moon, fair, glimmering, vast, tranquil, and sweet. The tone, of course, becomes ominous and threatening as the poem progresses to its conclusion.
The sea is calm tonight.The tide is full, the moon lies fairUpon the straits; on the French coast the lightGleams and is gone; the cliffs of England stand,Glimmering and vast, out in the tranquil bay.Come to the window, sweet is the night-air!