Denise is still breathing after she appears to have been strangled to death by Paul. In fact, she may have just gone unconscious and drowned in the water after being pushed overboard.
When Paul pours blood on Danny and Terri, they are already stained with it before it touches them. In addition, after the blood "pours" on them, it leaves no new traces.
Paul Serone: They strike, wrap around you. Hold you tighter than your true love. And you get the privilege, of hearing your bones break before the power of embrace causes your veins to explode.