Exegesis:

kai esontai sēmeia ‘and (then) there will be signs,’ i.e. probably after the times of the Gentiles (cf. Lagrange). For sēmeion cf. on v. 7 and reference there. The event to which the signs here point is described in v. 27.

en hēliō kai selēnē kai astrois ‘in sun and moon and stars,’ without article and hence denoting together the sky in its entirety. selēnē and astron.

kai epi tēs gēs sunochē ethnōn ‘and on earth (there will be) anguish of the nations,’ with estai understood, i.e. the nations will be in anguish. epi tēs gēs here different from v. 23.

sunochē ‘anguish,’ ‘dismay,’ ‘distress’ (cf. sunechō 4.38).

en aporia ēchous thalassēs kai salou lit. ‘in perplexity of the sound and the rolling of the sea,’ i.e. because of a perplexity due to the sound and the rolling of the sea. thalassēs may go with ēchous or with both ēchous and salou. The latter is preferable.

aporia lit. ‘being at a loss,’ ‘bewilderment,’ ‘perplexity.’ Together with what follows it takes up and explains sunochē.

ēchos ‘sound,’ ‘noise,’ ‘roaring.’

salos ‘rolling or tossing motion, especially of waves.’

Translation:

There will be signs. A verb like ‘appear/be-seen/become-visible’ may better fit the noun here.

Distress of nations in perplexity, or, ‘nations will be distressed, because they are perplexed,’ or simply, ‘nations will be distressed and perplexed.’ Some versions treat the two nouns as a hendiadys, e.g. ‘perplexed distress,’ ‘desperate fright’ (Nieuwe Vertaling). Nations probably refers here both to the Gentiles and to the Jewish people. The concept perplexity may be expressed by such idioms as ‘the heart jumps up’ (Dan), ‘speech vanishes’ (Malay), ‘spirit/mind at-its-end’ (Toraja-Sa’dan, cf. also English “at their wits’ end”), ‘no longer knowing what to do’ (Sranan Tongo), ‘tying up the head’ (Zarma); cf. also on 9.7.

At the roaring of the sea and the waves, or, taking ‘sea’ with both other nouns (see Exegesis), ‘at the roaring and the rolling of the sea,’ ‘because the sea is roaring and (its waves are) rolling.’ The expression refers to excessive sound and movement of the sea. The movement, being the producer of the sound, may better come first, cf. The Four Gospels – a New Translation‘s “surge and thunder of the sea”.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.