Sounds like creeping jenny to me.

maybe water celery? not really a vine but has long stems. The golden jenny's leaves are rather round.

:) MaryO

Since you said the flower looks like a buttercup, I looked up buttercup. The leaves of the creeping buttercup do resemble parsley. Is this it?

By the way, there are some very strange definitions for buttercup.

Here is a link that might be useful: Creeping Buttercup

I live in Texas and right now my pond is being taken over by Duckweed and some sort of vine that I am trying to figure out how to get rid of. Only problem is I haven't a clue of what the vine is. It is growing all arount the outskirts of the pond and also out into it. We have manually removed it from the pond but "manually" it will be impossible to get it out of the dirt around the edges of the pond. I have seen no flowers on it and it floats on top the water about every four or five inches or so there is what I would say looks like a rose bud but it is just leaves. Underneath it has kind of hairy roots if you will and these white spongy like roots. I need help fast and I have a picture of it, but I guess I cannot post the pic unless I know what it is, kind of useless to not be able to do so. If somebody can help me figure out how I would post a pic. Thanks

Water celery has white flowers that look like queen anne's lace