Middle voice of intransitive?

Hi!

I was wondering whether Ancient Greek had middle voice forms of
intransitive verbs.

The question arose when I asked myself whether the English sentence

  'I don't swim.'

which is translated as 'I cannot swim' into German (it the right
context), was middle voice.

English has not overt marker for middle voice, of course.  But to me,
it feels like that, because 'swim' in the active voice has an
implicit, here reflexive causation/volition/agent, namely the subject
itself.  Because middle voice deletes the semantic agent (usually
promiting the object to subject, which would be impossible for
intransitives), I was wondering whether 'I don't swim' could be
analysed as middle voice, and whether Ancient Greek had cases where it
was overtly marked.

Bye,
  Henrik