In the poem Night, the sea is depicted as a powerful, energetic force that is gradually quieted as Night descends. During the day, the sea embodies vitality - its waves crash, its currents move, it pulses with natural energy. But as Night falls, even this mighty force is subdued. The sea's restless motion is stilled or softened under Night's dominion, and its roaring gives way to a calmer, more subdued state.
The poet uses the sea to illustrate Night's overwhelming power: if even the vast, ceaselessly moving ocean can be tamed by darkness, then Night's authority over the natural world is complete. The sea is not presented as a place of celebration, nor as a metaphor for human struggle, nor as a neutral bystander. It is an active, vital part of nature that Night conquers and quiets.
The correct answer is that the sea is a symbol of natural vitality subdued by Night. It represents the living energy of the natural world being brought under the calming, silencing influence of darkness, reinforcing the poem's portrayal of Night as an all-encompassing force.