Final answer:
The sentence provided is in the passive voice, where the action of throwing is being done to the subject, the beach ball, by the blonde surfer.
Step-by-step explanation:
The sentence 'The beach ball is thrown by the blonde surfer.' is in the passive voice. In passive voice sentences, the subject is acted upon by the verb. The focus is on the action happening to the subject, rather than on who or what is performing the action. In contrast, active voice sentences have the subject doing the action. For example, in the active voice, the sentence would be 'The blonde surfer throws the beach ball.'