Thank you for your help. I think I made a mistake in my previous post (sentence 1). I added a few more examples I'm unsure of.
1) There is no point in (not of) worrying about his behaviour. He won't change it. It is no use/no good worrying about his behaviour. It is pointless/useless to worry .. (?)
2) I was amazed at seeing so many flowers in front of me (at being surrounded by so many flowers).
3) I'm opposed to keeping animals in captivity.
I was surprised at his passing his exam.
4) It is useless thinkiThe little dog scamped off when I tried to catch it.
The ducks were waddling in the pond.
The owl swooped down (I need to complete the sentence).
5) The pig rooted about for food (I don't think it's possible).
6) The mouse scurred away when it saw the cat coming up to him. (it??)
The place was swarming with bees.
Bees were swarming in the house.
I was surprised at his passing his exam.
OR I was surprised that he passed his exam.
4) It is useless thinki <~~INCOMPLETE
The little dog scampered off when I tried to catch it.
The ducks were waddling across the grass.
The ducks were swimming in the pond.
The owl swooped down and caught the mouse.
5) The pig rooted around for food
6) The mouse scurred away when it saw the cat coming up to him.
The place was swarming with bees.
Bees were swarming in the house.