There are at least two interpretations of Ophelia's death. The two most common theories are that she suffered an accidental death and the other theory was that she committed suicide. Before I go into these theories it's important to know that Ophelia was suffering from "madness" and it was not known if it was grief-induced from losing her father and then Hamlet rejecting her or if she was faking her "madness" like it was speculated of Hamlet. If she truly was grief stricken it makes sense that she might have turned to suicide. Losing her father and also having the person she was in love with tell her that he would not be with her may have pushed her over the edge and broken her leading her to think death was the only way out of her madness.
