U pješčanik nosimo kanticu i lopaticu.

Because Croatian uses different cases after u depending on meaning:

• u + accusative = movement into / to
• u + locative = location in / inside

Here, the sentence talks about carrying things to/into the sandbox, so pješčanik is in the accusative: u pješčanik.

Compare:

• Idemo u pješčanik. = We are going to/into the sandbox.
• Igramo se u pješčaniku. = We are playing in the sandbox.

Nosimo is the 1st person plural present tense of nositi.

So it means:

• we carry
• we are carrying
• sometimes, depending on context, we take

In this sentence, the most natural English translation is something like we carry / we are taking a bucket and a shovel to the sandbox.

Because Croatian often leaves out subject pronouns when they are already clear from the verb ending.

The ending -mo in nosimo already tells you the subject is we.

So:

• nosimo = we carry
• mi nosimo = we carry, but with extra emphasis on we

Croatian does this a lot, much more than English.

They are in the accusative singular, because they are the direct objects of nosimo.

Their basic dictionary forms are:

• kantica = bucket / little pail
• lopatica = little shovel / spade

For many feminine nouns ending in -a, the accusative singular ends in -u:

• kantica → kanticu
• lopatica → lopaticu

So the sentence is using the correct object forms.

It actually is in the accusative, but masculine inanimate nouns often look the same in the nominative and accusative singular.

So:

• pješčanik = nominative
• pješčanik = accusative

Same form, different function.

That is why u pješčanik is accusative even though the word itself does not visibly change.

Yes, they have a diminutive feel, especially in this context.

• kantica suggests a small bucket / pail, often a child’s bucket
• lopatica suggests a small shovel / spade

That fits very naturally with a sandbox sentence.

In practice, these are also very common everyday words, so they do not always feel especially “cute” or expressive. They can simply be the normal words for the small play objects children use.

Croatian word order is more flexible than English word order.

The sentence could also be:

• Nosimo kanticu i lopaticu u pješčanik.

Starting with U pješčanik puts the destination first, a bit like:

• To the sandbox, we’re carrying a bucket and a shovel.

So the original sentence is natural; it just gives slight emphasis to where the things are being taken.

Because Croatian does not have articles like English a/an and the.

So:

• kanticu can mean a bucket or the bucket
• lopaticu can mean a shovel or the shovel
• pješčanik can mean a sandbox or the sandbox

The exact meaning comes from context.

Nositi is an imperfective verb. It is used for:

• ongoing action
• repeated action
• general action without focusing on completion

So nosimo fits well for a simple scene like we’re carrying/taking these things to the sandbox.

A perfective verb would sound more focused on the completed result of bringing something somewhere. At an early learning stage, it is enough to notice that nosimo presents the action as an action in progress or as a simple general present.