"We are having dinner along the water."
Translation:Wir haben Abendessen am Wasser.
entlang is only used when there is movement. So you could use entlang to say "we are walking along the water" (wir gehen am Wasser entlang)
but since eating lunch does not involve movement, you would use the preposition "an" . so you would translate "we are having dinner along the water" as "wir haben Abendessen am Wasser" (am = an + dem)
IMO, a clearer translation of this preposition is to say "we are having dinner ON the water"
Nevertheless, there are many English sentences that feel thoroughly natural to me where having dinner "on the water" implies being near it - lakeside, beachside, etc. "On" in English feels like it implies a more formal / fancy dining experience than "by."
The family can go and have a picnic by the water, or they could go to the 5-star restaurant "on" the water (which is actually not literally on the water, but merely close to the shore).
I see that 'along the water' is still the supposed answer. That is a rubbish sentence. Nobody eats their dinner along the water. They might eat BY the water, but along the water makes no sense. Please hurry up and change this silly sentence for a sensible one in order to help the students.
I am a native English speaker and I cannot think of any time that I would say in English 'We are having dinner along the water.' I did get the German answer correct but that is a rubbish question. Please either change it to something more sensible or remove it. I cannot think of an appropriate alternative to suggest because I cannot work out what you are trying to say.
Die deutsche Variante des Satzes macht überhaupt keinen Sinn, besser wäre hier "Wir essen am Wasser zu Abend." Der Satz würde bei Muttersprachlern noch durchgehen. Denn es ist durchaus üblich, zu Abend bzw. zu Mittag zu essen. Aber "wir haben am Wasser Abendessen" geht gar nicht.