Questions & Answers about Hajen svømmer langsomt rundt i havet.
Why is there a -t at the end of langsomt?
In this sentence, the word describes how the shark swims, making it an adverb. In Danish, you form most regular adverbs by adding a -t to the basic adjective (langsom). It works just like adding "-ly" to "slow" in English.
Could I just say rund instead of rundt?
No, because rund is an adjective describing the shape "round". By adding the -t, it becomes the adverb rundt, which translates to "around" in English. Together with the preposition i, rundt i describes moving about within a space.
Why is the preposition i used here? Could I say på havet instead?
You use i havet because the shark is physically submerged in the water. If you used på havet (on the sea), it would imply being up on the surface, which is the phrasing you would use for a boat or a ship.
Both nouns have the definite "the" suffix, but one is hajen and the other is havet. Why the difference?
This comes down to the grammatical gender of the root nouns, which you just have to memorize. "A shark" is a common gender noun (en haj), so it takes the -en suffix to mean "the shark". "A sea" or "ocean" is a neuter noun (et hav), so it takes the -et suffix.