Actually, the pair there that sounds completely identical is о́зеро (Nom / Acc Sing) and о́зера (Gen Pl), both IPA [ˈozʲɪrə], /ó·zee·ra/.
In озё́ра the stress shifts to the second syllable, as indicated by the ё, leaving the о unstressed, thus sounding more like an а; IPA [ɐˈzʲɵrə], /a·zyó·ra/.
In brief, roughly:
- о́зеро ≈ ózeera
- озё́ра ≈ azyóra
As others have mentioned, this isn't grammatically correct. You need either "The" before "lake" or replace lake with "It's". Examples: "The lake is there" or "It's there". "It" would of course be based on context between the speakers; that is "it" is implying you are referring to the lake.
However, to me "It's there" can sound sarcastic. Or if when someone asks where a lake is (and they are having trouble finding it) the person answering responds "It's there" which comes across like "I don't know what else to tell you, but it exists" and/or "It's a lake, it can't move" and/or "It's so big you can't miss it". Saying "The lake is there" (while could also be said sarcastically depending on tone) would more likely be said from someone pointing it out.
Although, I wouldn't say I've never heard the "The" article never dropped, it's probably more common for !e to hear it said in an inquisitive and/or surprised manner and when speaking to someone informally, e.g., "Lake's there?!" [perhaps it's over a steep hiking trail one is reluctant to go over]; heard when in a hurry, e.g., someone passing by is looking for a store that's a few hundred feet in front of them "Store's there!"; and some other scenarios as well.
These subtle examples are fantastic.
The nuances of all this would be daunting to learn in a second language... and indeed, Russian seems to involve a degree of available nuance similar to that of English - depending on circumstance, vocal inflection, etc. It's a fun challenge, and I love how these forums sometimes provide extra info about some of that contextual nuance.
The article can usually be "the" or "a" for English nouns (excluding personal names). However "a" is used for singular items. Example: "I have a car" = "I have one car". "The" can usually be used for singular and plural. Example: "I have the car key" or "I have the car keys".
The articles in English, a/an and the are required before singular count nouns always. Example: a rose, the rose. "A rose by any other name would smell as sweet." Talking about roses in general. "The rose smells sweet." Talking about a specific rose.
Technically, countable, singular nouns must have a quantifier, no exceptions.