Translation:Are there many animals swimming in the North Sea?
But why in this case We have to use "swimming" in English version. I thought it is like with other construction with "staan, liggen, zitten"... Wouldn't it be rather more proper in English to ask: "Are there many animals in the North Sea?"? It is sort of obvious that they are swimming there (beside few species fixed to the ground or crawling there). Is this question in Dutch exactly about those animals which are swimming or just all that are there? I would be pleased to know your answer.
I believe in this case the swimming matters, not that the emphasis is on it but just that it's there and needs to be translated.
Just like "when will you be flying back?" vs "when will you be going back?". The flying is just used casually because that is the way the person will be going back home, but it isn't about the flying.
Hope you understand the nuance I'm trying to explain.
That would be
Zwemmen veel dieren in de Noordzee?
Slightly different meaning.
In the original it's about the North sea and if it has many animals swimming in it.
In your sentence it's about the animals and about the amount of them that swim in the North sea.
Hope this helped
The sentence you wrote would be written as follows in Dutch:
Zijn er veel dieren, die in de nordzee zwemmen?
You could argue that the English "many animals swimming" and "many animals that swim" are close enough to each other that both should be counted correct.
Nevertheless, they are different grammatical structures with corresponding different structures in Dutch.