In terms of the simplicity Classical prose would have favoured, I couldn't improve on the first two sentences of Phil's.
As regards his third, I am sceptical about quantum followed by the ablative. When quantum is used as an interrogative pronoun, it means "how much?" and can be followed by a partitive genitive in the singular. Since we deal with a plural here, one should use "quot" followed by the nominative, i.e.
nescio quot naves fuerint.
As regards Episcopus' efforts...
in (1) you will not see an interrogative particle precede the interrogative imperative, especially not when the actual question is to follow. Indeed, too, it is nice to use a deponent verb, yet the form required here would be vereare (or verearis) and it tends not to enjoy standing on its own in a non-participial sense.
in (2) your syntactical tomfoolery continues; a sentence ending in an interrogative particle (a sentence, that is, with verbs)? In fact, I think it is impossible to put the three words of your sentence in a more impossible word order!
I am puzzled all the more by (3)..."I do not know how great the long ships were"? The only, albeit ambitious, thing which I can imagine you were going for was "I do not know how great, with respect to their length, were the ships" (although that is rather different from the question asked) which would just want an accusative of respect, longum.
I can only hope from your erratic type at the end, that crapulence explains your erring from usual form?