Final answer:
The word 'returned' is a past participle in the sentence.
Step-by-step explanation:
The past participle in the sentence is 'returned'. A past participle is a verb form that usually ends in 'ed' or 'en' and is used to form verb tenses. In this sentence, 'returned' is the past participle of the verb 'return' and it describes the action of the group. It indicates that the group has already completed the action of returning to the dock.
Learn more about past participle usage in English sentences