Tässä on vettä, ole hyvä.

Tässä usually means here in a sentence like this.

Grammatically, it comes from tämä (this) plus the inessive ending -ssa / -ssä, which often means in. So historically it is something like in this.

In modern Finnish, though, tässä is very commonly used as a simple here, especially when something is near the speaker or being handed to someone.

So in Tässä on vettä, tässä means something like:

• here
• right here
• here you have

On is the 3rd person singular form of olla, which means to be.

So Tässä on vettä literally has the structure:

• tässä = here
• on = is
• vettä = water / some water

Finnish normally needs a verb in a full sentence, just like English does. So you cannot usually leave out on in a neutral sentence like this.

This pattern, [place] + on + [thing], is very common in Finnish for introducing or presenting something:

• Pöydällä on kirja. = There is a book on the table.
• Tässä on kahvia. = Here is some coffee.

Because vettä is the partitive singular of vesi (water).

Finnish uses the partitive very often with:

• uncountable substances
• an indefinite amount
• something being offered or presented as some

So vettä here means some water rather than the water or water as a complete, definite item.

That is why Tässä on vettä is natural when offering someone a drink.

Compare:

• Tässä on vettä. = Here is some water.
• Tässä on vesi. = Here is the water / Here is the water portion.

The second one is possible in some contexts, but it sounds more definite and less natural for a general offer.

It is a very common presenting/existential-type sentence.

Instead of starting with the thing itself, Finnish often starts with the location or the place where something is available, and then introduces the thing:

• Tässä on vettä.
• literally: Here is water.

This is why the word order may feel different from basic textbook patterns like subject + verb + object.

In this sentence, Finnish is not really saying The water is here in the same way as English might. It is more like Here is some water or There is some water here, depending on context.

Here, ole hyvä means something like:

• here you are
• please
• there you go

Literally, it is made from:

• ole = imperative of olla (be)
• hyvä = good

So word-for-word it looks like be good, but that is not how you should translate it in this situation. It is an idiomatic polite expression.

When someone hands you something, ole hyvä is very common.

So:

• Tässä on vettä, ole hyvä.

means something like:

• Here is some water, here you are.

No. Ole hyvä has a few common uses.

It can mean:

• here you are / there you go when giving something
• please in some polite situations
• you’re welcome after kiitos

Examples:

• Tässä, ole hyvä. = Here you are.
• Istu, ole hyvä. = Please sit down.
• Kiitos. – Ole hyvä. = Thank you. – You’re welcome.

So the exact English translation depends on the situation.

Ole hyvä is the singular imperative form, so it is used with one person.

It is neutral and polite in normal everyday speech.

If you are speaking to:

• more than one person, or
• using the more formal/polite plural form,

you would say olkaa hyvä instead.

So:

• Ole hyvä = to one person
• Olkaa hyvä = to several people, or more formal/polite

Both can often be translated as here, but they are not exactly the same.

Tässä usually means:

• right here
• in this spot
• at hand
• something close and immediate

Täällä usually means:

• here in this place/area
• here around here

So in a sentence where you are offering or handing someone something, tässä is more natural:

• Tässä on vettä. = Here is some water.

If you said Täällä on vettä, it would sound more like:

• There is water here / Water is available here in this place

So tässä fits the immediate, presentational meaning better.

The comma separates two parts:

• Tässä on vettä = Here is some water.
• ole hyvä = here you are / please.

In speech, there is usually a small pause between them, so the comma is natural.

You could also write or say it in slightly different ways:

• Tässä on vettä. Ole hyvä.
• Ole hyvä, tässä on vettä.

All of these are understandable. The version with the comma feels like one smooth polite offering.

Yes, but the meaning or emphasis may change.

The most natural neutral order here is:

• Tässä on vettä.

This presents the water to the listener.

You could also say:

• Ole hyvä, tässä on vettä.

That sounds very natural too, with ole hyvä first.

A more unusual order like Vettä on tässä is possible only in special contexts, for example if you are contrasting here with somewhere else. It is not the normal way to offer someone water.

So for a learner, Tässä on vettä is the best basic pattern to remember.