Ophelia is portrayed by Hamlet as a very calm, but troubled young lady in the beginning of the book. She has her problems, but she deals with them in a very lady like way. As it gets closer to the death of Laertes, Ophelia seems to be effected heavily by this. Then once it gets closer to her own death, she begins to act a little bit crazier than normal. The sense of suicide is left once we realize that Ophelia is dead.
In the painting, Ophelia looks very hopeless. It looks like she drowned, but don't most people face down when they drown. Her being faced up adds to the suspense. I still think that suicide was the way she died, but the painting adds a matter of suspense to the girl's death.
Now in the films, I think that Ophelia's death is the death. The visual of her going insane makes everything better. My understanding of her death is clearer after seeing the film versions. Also, the variety of ways her attitude is portrayed in each makes it better as well. In one scene, she's very creepy. In another, she's in a straight jacket to add to the insanity. In the first, she was just over the top as well. The common thing I found though was, she just disappeared with no one knowing. This also adds to her committing suicide. I think the films were the best way to show Ophelia's death, it's portrayed well and it puts the best image in my head.