kousokusen mo kekkousita tame, yoyakutorikesi wo kime zaru wo enai.

高速船 literally means high-speed boat/ship. In many travel contexts, it is best translated as high-speed ferry.

• 高速 = high speed
• 船 = boat / ship / vessel

So in this sentence, it refers to a fast passenger boat service.

も means also / too.

So 高速船も欠航した suggests that the high-speed ferry was also canceled, probably in addition to something else already mentioned or already understood from context.

The nuance is:

• not just one thing was canceled
• the ferry too was canceled

Without も, it would simply state that the ferry was canceled, with no sense of addition.

Good question. 欠航 is often associated with airplanes in beginner materials, but it can also be used for other scheduled transport services such as ferries.

It means a scheduled service was canceled and did not operate.

A useful comparison:

• 欠航: cancellation of a scheduled voyage/service, especially planes or ships
• 運休: suspension/canceled operation, especially for trains, buses, etc.

So for a ferry, 欠航した is perfectly reasonable.

Here, ため means because of or due to.

So:

• 高速船も欠航したため = because the high-speed ferry was also canceled

This use of ため is a fairly formal or written-sounding way to show cause/reason.

Compared with other common forms:

• から = because; more direct and conversational
• ので = because; softer and common
• ため = because/due to; more formal, written, explanatory

So this sentence sounds somewhat formal or report-like.

予約取消 is a noun-like, formal, administrative expression meaning reservation cancellation.

It is made from:

• 予約 = reservation
• 取消 = cancellation

In everyday Japanese, people often say:

• 予約を取り消す = to cancel a reservation
• 予約の取り消し = cancellation of a reservation

So 予約取消 feels more compact and bureaucratic, like wording you might see in notices, forms, or business writing.

Because 予約取消 is functioning as the object of 決める.

The sentence structure is basically:

• 予約取消を決める = to decide on cancellation of the reservation

Even though 予約取消 is a noun, nouns can still take を when they are the direct object of a verb.

Compare:

• 旅行を決める = decide on a trip
• 方針を決める = decide on a policy
• 予約取消を決める = decide on canceling the reservation

ざるを得ない is a set grammar pattern meaning:

• cannot avoid doing
• have no choice but to do
• must, reluctantly

It attaches to the nai-stem of a verb:

• 行く → 行かざるを得ない
• 読む → 読まざるを得ない
• 決める → 決めざるを得ない

Important special case:

• する → せざるを得ない

This expression sounds more formal and often carries a nuance of reluctance or inevitability.

So 決めざるを得ない means:

• have no choice but to decide
• must decide, whether one wants to or not

This is an excellent question, because it gets at nuance and naturalness.

The sentence as written says something like:

• have no choice but to decide on canceling the reservation

That focuses on the decision.

If you say:

• 予約を取り消さざるを得ない

that means:

• have no choice but to cancel the reservation

That focuses on the action itself.

In many contexts, 予約を取り消さざるを得ない would sound more natural in everyday Japanese. The given sentence sounds more formal and somewhat indirect, as if talking about making the decision rather than performing the cancellation itself.

It is understandable, but it is a bit stiff and not the most natural everyday phrasing.

More natural alternatives would often be:

• 高速船も欠航したため、予約を取り消さざるを得ない。
• 高速船も欠航したため、予約の取消を決めざるを得ない。

Why?

• 予約取消 as a bare compound sounds administrative
• 予約を取り消す is more natural in ordinary speech
• 予約の取消 sounds more standard than 予約取消 if you want a noun phrase

So the original sentence is not wrong, but it feels formal and somewhat compressed.

Because the sentence is describing two different time relationships:

• 欠航した = the ferry was canceled already
• 決めざるを得ない = as a result, someone now has no choice but to decide

So the cancellation happened first, and that past event creates the present necessity.

In English, we often do the same thing:

• Because the ferry was canceled, we have no choice but to cancel the reservation.

So the tense mix is normal.

The subject is omitted, which is very common in Japanese.

Depending on context, it could mean:

• I have no choice
• we have no choice
• the customer has no choice
• the company has no choice

Japanese often leaves the subject unstated when it is clear from context. So the listener or reader is expected to infer it.

It has a fairly formal, written, somewhat businesslike tone.

That comes from several features:

• ため instead of a more casual から
• 予約取消 as a compact administrative noun
• ざるを得ない, which is formal and stiff compared with simpler expressions

A more conversational version might be something like:

• 高速船も欠航したので、予約を取り消さないといけない。

That is less formal and more natural in everyday speech.