Answer:
Alliteration.
Step-by-step explanation:
Alliteration is a literary device used by writers in which a number of words that have the same consonant letter at the beginning of the words are repeated successively or in close association with each other. In the sentence "Sandy sinks to the shore silently", we have a series of words that began with the consonant "s", "Sandy, sinks, shore, silently". This is an example of alliteration.