"What will you do when you see the crocodile?"
Translation:Kion vi faros kiam vi vidos la krokodilon?
I still get confused with tenses. I can see that “will you do” is “vi faros” but I cannot see why the “you see” is not present tense (“vidas”). After all, as soon as I know that I am going to a zoo to see crocodiles, I will see a crocodile! So, the question in Esperanto seems to be about what you are going to do when you find out that you are going to see a crocodile rather than what you are going to do when you actually see one.
Is this one of those rare cases where the English is more logical than the Esperanto? ;-)
No. This is a confusion because English doesn't really have a proper future tense, and so in English we tend to put a lot of future actions in present tense. It's a bit of a mess.
The whole thing is: What will you do when you (will) see the crocodile. Or put another way: What are you going to do when you (are going) to see the crocodile.
You are going to see the crocodile in the future so you "will see" or "are going to see" (vidos) it. Take the sub-clause by itself and you see why the Esperanto makes more sense than the English:
Mi vidos la krokodilon. (I will see the crocodile/I am going to see the crocodile.)
Mi vidas la krokodilon. (I see the crocodile [I am looking at the crocodile right now]).
The English only seems more logical to us because it's our native language.
No, it has to be "Kion" because it's the object of the sentence, that is, it is the thing having the action done to it - it's "done" by "you". Supposing the answer was, "I will do my homework". In Esperanto that would be, "Mi faros miajn hejmtaskojn, " because the homework is being done by you. Similar, the "What" in the question represents the thing you are going to do, so in Esperanto, it must be "Kion".