The best figurative meaning for the word watermarks as it is used in the context of paragraph 5 is

An adverb clause is the answer?

Singular third person pronouns are “he,” “she,” “it,” “his,” “hers,” “him” and “her,” and third person plural pronouns are “they,” “them” and “their.” the number of people to which you are referring should always match the pronoun you choose (“he” to refer to one male, “they” to refer to more than one male).