Water saturated Bougainvillea
Our plant unfortunately has been sitting in excess water, drain blocked. The leaves are all fallowing off. I have it now potted so it can drain. It is still quite moist. Not sure what direction to go with this. We live in Maryland so it is in a pot. Too cold here.
I'm not sure how large of a container that you are working with, but hopefully if it's large you can get some help to work on your plant.
I would lift the plant from the container and remove the wet soil and check the roots for signs of root rot.
You can prune the dead portions of the roots.
The pot can be cleaned and new soil used to repot the plant.
The plant may need to be cut back if it continues to decline. Follow the pruning instructions in the link below.
These articles have more information on over watered plants.