The phrase "the Sun was shining on the sea" primarily employs imagery as its figurative language. Imagery involves using descriptive language to create a visual representation in the reader's mind, appealing to the senses.
Additionally, one could argue it contains personification, as it suggests a more dynamic relationship between the sun and the sea, implying that the sun is actively shining, which creates a vivid picture of a bright, sunny scene. However, the primary effect is likely the imagery created by the description.