Sorry, a very atypical angle because it flew into a tree and this is the underside. But you can just make out the edges of the black eye mask.
I've added a pic from a close-up of the flower and a recent pic showing more growth. This has the celery-shaped leaf (no different-shaped leaves underwater), tall central stem and appropriate flower to be 'celery-leaf buttercup' aka 'cursed crowfoot'.
Climbing bittersweet; why it sucks, and why we should stop it