An adverb is a descriptive word that modifies a verb. 'Soaked'
does not modify a verb (eg the sentence "Dave soaked glanced at
Karen, who melted" does not make sense, because 'soaked' isn't an
adverb), and therefore is not an adverb. In a sentence that uses
'soaked': "Dave soaked Karen at the water gun festival, and
thereafter she was soaked," 'soaked' is used first as a past-tense
verb, and second as predicate adjective modifying 'Karen.'
Therefore, one may conclude that 'soaked' is not an adverb.