Why not "survolent" - meaning to fly over. It is more modern!
Yes, "survolent" is very good, not because it is modern (it is not), but because it is more elegant.
I added it. Thanks.
Is there any reason why « la mer » isn’t accepted?
Yes, there is: "la mer" is "the sea".
And why not "sur"?
"Sur" basically suggests a contact with the object.
why not du ocean
Because océan begins with a vowel so, for the sake of elision, du becomes de l'.
Volent is not shown in the dictionary.
It's the third person plural conjugation of the verb voler - to fly
I thought nouns that started with vowels used l' instead of le or les? Why is't it l'oiseaux?
Oiseaux is plural. I don't think you can use l' with plurals, only the singular.
Nouns that start with vowels use "l'" instead of "le" or "la". Their plurals still use "les".
I selected "l'" for l'ocean, but was told that I had not put it in. This happened twice.