Could I die if water was injected into my bloodstream?

Yes. Doctors use sterile water injections into the bloodstream on a regular basis, and this is perfectly safe. However, nonsterile water (tap water) injected into the bloodstream may be contaminated with chemicals and bacteria that could lead to infection and death. Bottom line: let your health care professional do all injections into your bloodstream!
Not if it is sterile. Since out blood is 99+%h20, the water in the bloodstream is not the concern- how it got in there, and how sterile it is would be the worry! we give IV fluids to patients on a daily basis to help them get well and feel better. The volume of the water might also be a problem, but again, not the water itself.