object complement or adjective phrase?

Hi,

Please tell me if the underlined parts are object complements or adjective phrases describing the objects. I think some responses to these said that they are object complements but I think they are adjective phrases modifying/describing the objects. Some are from this forum.

I saw the girl pour the water down the sink. (What girl? the girl pouring the water down the sink)

I saw them running away. (Who did you see? I saw them -- the people who were running away)

That is the box to be thrown away. (What box? the box that to be thrown away)