Is "ambulabat" a present participle in the imperfect?

Question

This passage is from Matthaeus 14:29 of the Latin Vulgate. I've included much of the surrounding text because the lack of punctuation makes it difficult for me to distinguish the sentence structure.

respondens autem Petrus dixit Domine si tu es iube me venire ad te super aquas 29 at ipse ait veni et descendens Petrus de navicula ambulabat super aquam ut veniret ad Iesum 30 videns vero ventum validum timuit et cum coepisset mergi clamavit dicens Domine salvum me fac 31 et continuo Iesus extendens manum adprehendit eum et ait illi modicae fidei quare dubitasti 32 et cum ascendissent in naviculam cessavit ventus 33 qui autem in navicula erant venerunt et adoraverunt eum dicentes vere Filius Dei es

This can be seen at: http://biblehub.com/vul/matthew/14.htm

Am I correct in determining that the word "ambulabat" is here used as a present participle in the imperfect sense?

Answer 1

Unless there's some bizarre, ultra-special construction going on here, ambulabat can never be a present participle -- it is the 3rd person singular, imperfect active form of ambulare, and can be translated as was walking.

Answer 2

Punctuation and macrons might help:

Respondēns autem Petrus dīxit, "Domine, sī tū es, iubē mē venīre ad tē super aquās."
[29] At ipse ait, "Venī!" Et dēscendēns Petrus dē nāviculā ambulābat super aquam ut venīret ad Iēsum.
[30] Vidēns vērō ventum validum timuit et cum coepisset mergī clāmāvit dīcēns, "Domine, salvum mē fac!"

Answering, Peter said, "Lord, if you are, order me to come to you over the waters."
[29] But he [Jesus] said, "Come!" And climbing down from the little ship, Peter was walking across the water in order to come to Jesus.
[30] Seeing a strong wind, though, he became fearful, and as he began to sink, he cried out, saying, "Lord, save me!"

Possibly ambulabat is in the imperfect tense to indicate that Peter didn't finish walking: fear overcame him before he got all the way across the water.