Kuna samaki wengi baharini.

Kuna is a very common Swahili word meaning there is or there are.
In Kuna samaki wengi baharini, it introduces the existence of something, so the sentence literally starts like There are...

It does not change for singular vs. plural the way English does. The noun and context tell you whether the meaning is there is or there are.

Examples:

• Kuna mtu nje. — There is a person outside.
• Kuna watu nje. — There are people outside.

In Swahili, some nouns have the same form in singular and plural, and samaki is one of them. It can mean:

• a fish
• fish

So you know it is plural here because of wengi (many) and the overall meaning of the sentence.

Compare:

• samaki mmoja — one fish
• samaki wengi — many fish

Wengi is the plural form meaning many for nouns in the animate class, which includes animals and people. Since samaki refers to fish, wengi is the correct agreement form.

Swahili adjectives and quantifiers often have to agree with the noun class of the noun they describe.

So:

• samaki wengi — many fish

If the noun belonged to a different class, the form of many would often be different.

Yes. In Swahili grammar, animals are commonly grouped with the animate noun class, the same class that includes people. That is why you get agreement like:

• samaki wengi — many fish

This is a grammatical category, not a statement that fish are human.

Baharini means in the sea or at sea.

It comes from bahari (sea) plus the locative ending -ni, which often means:

• in
• at
• on depending on context.

So:

• bahari — sea
• baharini — in the sea / at sea

This -ni ending is very common in Swahili for places and locations.

Examples:

• nyumbani — at home
• shuleni — at school
• mjini — in town

Because the idea of in/at is already built into baharini through the locative ending -ni. So Swahili often expresses location with the noun itself rather than with a separate preposition like English does.

That is why:

• baharini = in the sea

not usually something like in bahari.

The word order here is:

• Kuna — there is/there are
• samaki wengi — many fish
• baharini — in the sea

So the structure is basically:

There are + noun phrase + location

This is a very natural Swahili pattern for saying that something exists somewhere.

Yes, that is also possible, but it means something slightly different in emphasis.

• Kuna samaki wengi baharini = There are many fish in the sea.
  This focuses on existence/presence.
• Samaki wengi wako baharini = Many fish are in the sea.
  This focuses more directly on the fish themselves and where they are.

Both are grammatical, but kuna is especially common when introducing the idea that something exists somewhere.

In practice, it means the location of the fish: There are many fish in the sea.
The locative phrase baharini tells you where the fish are.

Swahili often places location expressions after the noun phrase, much like English can place them at the end:

• There are many fish in the sea.

So it naturally reads as the place where the fish exist.

Yes. Kuna works with both.

Examples:

• Kuna samaki baharini. — There is a fish / There are fish in the sea.
• Kuna samaki wengi baharini. — There are many fish in the sea.

Swahili does not need a different form like English there is vs. there are.

You could say:

Kuna samaki mmoja baharini.

Here:

• samaki = fish
• mmoja = one

Because samaki can be singular or plural, mmoja makes it clearly singular.

A simple pronunciation guide is:

KOO-nah sah-MAH-kee WEHN-ghee bah-hah-REE-nee

A few helpful points:

• kuna → KOO-nah
• samaki → sah-MAH-kee
• wengi → roughly WEHN-ghee
• baharini → bah-hah-REE-nee

Swahili pronunciation is usually quite regular, and most letters are pronounced clearly.

Yes, a few things are especially worth noticing:

1. kuna covers both there is and there are.
2. samaki looks unchanged in plural, unlike English fish/fishes patterns learners may expect.
3. wengi must agree with the noun class, so you cannot just use one fixed word for many in every situation.
4. baharini includes the meaning of in through -ni.

So even though the sentence is short, it shows several important Swahili grammar patterns.