tibi is "to you" as an indirect object, which is not the situation we have in this sentence. Throwing something to (or towards) someone demands "ad" and an accusative of place to which.
I agree, I don't think the dative case should be used when describing physically throwing something
Precisely. We have to distinguish between "to" that means "motion towards" ( = ad + accusative) and "to" that means "in someone's interest, for someone" (= dative case, indirect object).
Maybe we should translate: "We throw the fish for you ( = on your behalf)".
It is also possible "iacere aliquid IN ALIQUEM"
"Iacere aliquid in aliquem", means to throw something to someone".
In aliquem, here is "vobis", and Aliquid is "piscem". So, I don't really understand your question.
He wants to construct it with preposition in + accus., as opposed to the dative.
Elsewhere I've suggested using ad + accusative, with iacere.
to throw...involves movement from one place to another...needs ad plus accusative, NOT dative case
Weird bug: Duolingo offered only "iacimus", then said I have a typo and it should have been "iaciumus".
How would you say, "we throw fish at you"?
there's no way to tell from the English that 'fish' is singular. It is translated into a Latin plural elsewhere. How are we supposed to guess?
In such situations, Duolingo should accept both possibilities as correct. If it does not, and you believe your answer is otherwise correct, then report it as "My answer should be accepted.".
How can a word "iacimus" be spelled wrong when it is YOUR word?
Cette manie de jeter le poisson!