"You have water."
Translation:Tá uisce agat.
Is "Tá uisce agat." the same as "Tá uisce agat?" The first is a statement and the second is a question. Am I just not far enough in my learning to know the difference?
No. To ask a question, you have to put the interrogative particle an before the verb. Because tá is an irregular verb, the question form is an bhfuil.
An bhfuil uisce agat? - "do you have water?"
Why is tá in front instead of agat like you would in the sentence "Ólaim uisce"?
agat isn't a verb.
Irish doesn't have a verb for "have". To say "X has Y", you say Tá Y ag X.
When X is a pronoun (like "you") it is combined with the preposition ag.