A practical english grammar - Vyssaja skola 1978
SENSORY VERB + ING-FORM with subject
Sound symbols
The same verbs as those in Pattern 12a can also be followed by noun +ing-form. The difference in meaning between the base form and the ing-form in these constructions is exactly the same as the difference between the simple present tense (he works) and the present progressive phrase (he is working). The base form expresses an action that is completed, has not yet occurred, or happens habitually or characteristically; the ing-form expresses an action that is (or was) in progress.
I see him crossing the street.
She heard him opening the door.
I felt the insect crawling up my arm.
If the characteristic verb occurs as an ing-form, the subordinate verb is almost always a base form, regardless of the meaning. Two ing-forms are not used in the same construction.
I am watching the boys dive.
(Seldom: I am watching the boys diving.)
Ordinarily, as was pointed out on page 102, the subjects of gerunds may be either possessive or objective. In this construction, they are always objective.