Question

Which sentences below include only prepositional phrases (no participial or absolute phrases and no dependent clauses)? Select all that apply

Answer 1

I'm 90% sure the answer would be 2. Prepositional phrases contain no subjects or verbs. 
So, number two. (There was no one visible; under him, in the water, the dim shapes of the swimmers had disappeared.)

Answer 2

Answer:  There was no one visible ; under him, in the water, the dim shapes

of the swimmers had disappeared.

He could see nothing through the stinging salt water but the blank rock.