1 Wendy: The English galleon be gainin' on us! They be after Greybeard's treasure map!
2 Long Tom: Arrr! Luck be with us! The sun be settin', an' there be no moon. Belay them lanterns, ye scurvy swabs!
2 Dirque: Aye, cap'n!
3 {scene change: The English galleon in hot pursuit. The sun is setting slowly in the background and it's getting darker.}
3 Mate: We'll lose them in the dark. They're dousing their lights.
3 Ponsonby: We shall see by the light of our just and noble cause!
4 Mate: Just how much starch are they putting in your collars, captain?

Another one from the "Have you noticed" files:

Sunsets. In movies. Why do they always go from broad daylight to darkness in under 3 minutes of screen time? Haven't any movie directors ever heard of twilight?

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2017-06-04 Rerun commentary: That's actually a cool idea for a movie. The whole film takes place in real time, during twilight. The opening scene shows the sun setting, and all the action takes place during the extended twilight hours of some high latitude place like northern Europe, and as it ends the sky finally darkens to black.

For completeness though, there really are places where there's virtually no twilight. Twilight is when the sun is just a small distance below the horizon. Definition-wise, there are three degrees of twilight:

• Civil twilight - the centre of the sun is from 0° to 6° below the horizon. This is when the sun is down but the sky is still very bright. You can still make out objects, such as reading text, and can only see a handful of the very brightest stars and planets.
• Nautical twilight - the centre of the sun is from 6° to 12° below the horizon. The sky is in an intermediate darkening phase, and objects become indistinct - you can no longer read by natural light. In clear weather, you can make out the silhouette of the horizon against the sky. (This is the origin of the term "nautical" - sailors can still sight the horizon to navigate during nautical twilight.)
• Astronomical twilight - the centre of the sun is from 12° to 18° below the horizon. In this period it is close to fully dark. The horizon becomes indistinct and most stars become visible. It's called astronomical twilight because there's still enough scattered sunlight in the atmosphere to interfere with precise astronomical observations.

In the low latitudes of the tropics, the sun sets on a much more vertical path, so plunges below the horizon very quickly. The sun moves across the sky^[1] at a constant 15° per hour. So if it is setting vertically, it traverses the 6° of civil twilight in 24 minutes. This is from the sun still being half in the sky to it being too dark to read, in just 24 minutes. The Caribbean, where these pirates are, is in the tropics, so sunset here would actually be very quick and twilight would last only a short time.

At high latitudes, the sun's path through the sky is at more of an angle, and the sun travels more horizontally than vertically. So although it still traverses 15° in an hour, it might be 12° horizontally and only 9° vertically.^[2] This means it takes 40 minutes to traverse civil twilight. And the further north (or south) you go, the more shallow the angle of the sun and the longer twilight lasts. By the time you get to northern Europe, the various grades of twilight can last a few hours.

I recall when I visited England one summer, I was shocked and amazed by how long the twilight lasted, compared to back home in Sydney. The difference was very obvious.

[1] From our perspective. In reality of course the Earth is spinning at a rate of 15° per hour.

[2] Using Pythagoras' theorem.