Дети сидят на бревне у воды.

Дети means children. Its singular is ребёнок (child).

This is an irregular plural, so you cannot predict it from the singular in the usual way. A learner often expects something more regular, but ребёнок → дети is just a form you need to memorize.

A useful pair to remember is:

• ребёнок = child
• дети = children

Сидят is the 3rd person plural present-tense form of сидеть (to sit / to be sitting).

It is plural because the subject is дети (children), which is plural.

So:

• ребёнок сидит = the child is sitting
• дети сидят = the children are sitting

Russian verbs must agree with the subject in number, so дети requires сидят, not сидит.

This is a very common question.

• сидеть = to be sitting, to sit in the sense of being in a seated position
• сесть = to sit down, meaning the action of moving into that position

In this sentence, the children are already on the log, so Russian uses сидят from сидеть.

Compare:

• Дети сидят на бревне. = The children are sitting on a log.
• Дети сели на бревно. = The children sat down onto a log.

Because на can take different cases depending on meaning:

• на + accusative = motion onto something
• на + prepositional = location on something

Here the meaning is location: the children are already sitting on the log. So Russian uses the prepositional case:

• на бревне = on the log

If there were movement onto the log, it would be:

• сесть на бревно = to sit down onto the log

Бревне is the prepositional singular of бревно (log).

The noun бревно is a neuter noun ending in -о. In the prepositional singular, many such nouns change -о to -е:

• окно → на окне
• письмо → в письме
• бревно → на бревне

So на бревне literally means on the log.

У воды means by the water, near the water, or at the water’s edge, depending on context.

The preposition у usually means by, beside, near, or next to.

So:

• у воды = near the water

It does not mean in the water. If you wanted in the water, you would say:

• в воде = in the water

Because the preposition у requires the genitive case.

The dictionary form is:

• вода = water

After у, it changes to the genitive singular:

• у воды = by the water / near the water

So the pattern is:

• вода → воды

This is one of the basic things to learn with Russian prepositions: many of them always require a specific case.

Yes. You could also say:

• около воды = near the water
• возле воды = near the water

These are very similar in meaning to у воды. In this sentence, у воды sounds natural and simple.

Very roughly:

• у воды = by the water / at the water
• около воды = near the water
• возле воды = near the water

The differences are small here, and all can work depending on style and context.

Russian does not have articles like a, an, and the.

So Дети сидят на бревне у воды can mean:

• The children are sitting on a log by the water
• Children are sitting on a log by the water

Which English version is best depends on context. Russian usually leaves that information unstated unless something else in the sentence makes it clear.

Russian word order is more flexible than English word order because the case endings show the grammatical relationships.

So this sentence could be rearranged, for example:

• Дети сидят на бревне у воды.
• У воды дети сидят на бревне.
• На бревне у воды сидят дети.

These all have roughly the same basic meaning, but the emphasis changes:

• starting with дети focuses first on the children
• starting with у воды highlights the location
• starting with на бревне highlights where they are sitting

The original order is natural and neutral.

A helpful stressed version is:

Де́ти сидя́т на бревне́ у воды́.

A few pronunciation notes:

• де́ти = stress on the first syllable
• сидя́т = stress on the last syllable
• бревне́ = stress on the last syllable
• воды́ = stress on the last syllable

Also, unstressed о in Russian is often pronounced more like a reduced vowel, not a clear English o. So spoken Russian may sound a little different from what the spelling suggests.

Usually, yes. Grammatically, на бревне is singular, so it most naturally means on a log or on the log—one log.

If you wanted to say they were sitting on logs in general or on several logs, you would use a plural form, for example:

• на брёвнах = on logs

So the singular бревне points to one specific log in the scene.

This is a good spelling question.

The dictionary form is usually written бревно, and the plural is брёвна. The vowel can change with stress:

• бревно́
• на бревне́
• брёвна

In Russian writing, ё is sometimes omitted and replaced by е in many texts, but when learning, it helps to know where the stress really is. So you may see:

• брёвна written clearly with ё

while бревне has е because the form is different and the stress falls elsewhere.