Selagi menunggu kapal di pelabuhan, saya membaca buku kecil tentang laut.

Selagi means while or as/so long as in the sense of during the time that something is happening.

In this sentence, Selagi menunggu kapal di pelabuhan means while waiting for the ship at the harbor.

Compared with sementara:

• selagi often feels a bit more natural in everyday speech for while doing something
• sementara can also mean temporary or meanwhile, depending on context

So in this sentence, selagi is a very natural choice for introducing the background action.

Menunggu is the active verb form from the root tunggu (wait).

The prefix meN- is commonly used to form active verbs. With tunggu, it becomes menunggu.

So:

• tunggu! = wait! (command)
• saya menunggu kapal = I am waiting for the ship

In this sentence, menunggu works like waiting in English.

Yes, the most natural reading is that saya is also the person doing the waiting.

In Indonesian, when a sentence begins with a phrase like Selagi menunggu kapal di pelabuhan, the subject is often understood from the main clause that follows. So the sentence is understood as:

• While I was waiting for the ship at the harbor, I read a small book about the sea.

Indonesian often leaves the subject unstated in subordinate phrases when it is clear from context.

Because di here is a preposition meaning in / at / on, not a verb prefix.

So:

• di pelabuhan = at the harbor
• di rumah = at home
• di sekolah = at school

It is written separately when it marks location.

By contrast, di- is written together when it is a passive verb prefix:

• dibaca = is read
• ditulis = is written

That is a very important spelling rule in Indonesian.

Kapal usually refers to a ship or a larger vessel.
Perahu usually means a boat, often smaller.

So:

• kapal = ship / large boat / vessel
• perahu = boat / smaller craft

In a harbor context, kapal makes very good sense, because harbors are commonly associated with larger vessels.

In Indonesian, adjectives usually come after the noun they describe.

So:

• buku kecil = small book
• rumah besar = big house
• laut tenang = calm sea

That is one of the most basic word-order patterns in Indonesian:

• noun + adjective

It can translate as either small or little, depending on the context and the English style you want.

So buku kecil could be:

• a small book
• a little book

Usually, kecil primarily refers to size, so small is the safest basic translation.

It most naturally describes buku kecil.

So:

• buku kecil tentang laut = a small book about the sea

The phrase tentang laut tells us what kind of book it is. It does not usually mean that the reading itself was done about the sea; it is the book that is about the sea.

Tentang means about or concerning.

So:

• buku tentang laut = a book about the sea
• cerita tentang keluarga = a story about family

A similar word is mengenai, which also means regarding/about, but tentang is very common and natural here.

Indonesian does not normally use articles like English a, an, and the.

So:

• kapal can mean a ship, the ship, or just ship/ships, depending on context
• pelabuhan can mean a harbor or the harbor
• buku kecil can mean a small book or the small book

The listener figures it out from context rather than from an article.

Yes, aku could be used, but it would change the tone.

• saya = neutral, polite, standard
• aku = more informal, personal, casual

So:

• saya membaca... sounds standard and generally appropriate in many situations
• aku membaca... sounds more conversational and intimate

In learning materials, saya is often preferred because it is broadly useful.

The comma separates the introductory time clause from the main clause.

Structure:

• Selagi menunggu kapal di pelabuhan, = introductory clause
• saya membaca buku kecil tentang laut. = main clause

This is similar to English:

• While waiting for the ship at the harbor, I read a small book about the sea.

In Indonesian, commas are commonly used this way when a clause comes first.

Yes. Indonesian allows some flexibility.

For example:

• Saya membaca buku kecil tentang laut selagi menunggu kapal di pelabuhan.

This still means essentially the same thing: I read a small book about the sea while waiting for the ship at the harbor.

The original version puts the while clause first, which gives a nice sense of setting the scene before the main action.

Membaca specifically means to read.

So:

• membaca buku = to read a book
• membaca surat = to read a letter

If you want to say study, Indonesian would more commonly use belajar.

So in this sentence, membaca definitely refers to the action of reading the book.

It is very natural and grammatical.

It has a common and clear structure:

• time/background phrase first
• main clause second

Nothing in it sounds strange. It reads like normal written or careful spoken Indonesian:

• Selagi menunggu kapal di pelabuhan, saya membaca buku kecil tentang laut.

A learner can treat it as a good model for making similar sentences.