We slip back into the main narrative of Verbal's story, and see that the remaining rival gangsters on the boat are extra nervous…especially when one of them claims that Söze is on the boat, hunting them and killing them.
McManus and Keaton sneak around the boat, but can't find any of the cocaine that's supposed to be there—it apparently never was there.
We see Söze kill an old gangster—apparently Marquez—on the boat. Of course, we don't actually see Söze's face.
Verbal moves towards the boat, wielding a gun. McManus comes out with a knife in the back of his head, and falls over dead. He's been killed by Söze.
Söze then shoots Keaton from behind, and Keaton falls over—into the wounded position we saw him at in the beginning.
In the office, Verbal gets anxious, saying he knew Söze was the one who killed Keaton and he was too afraid to try to shoot Söze himself.
But back to the boat scene—from behind a pile of rope, Verbal sees Söze kill Keaton and light the spilled trail of gasoline on fire, causing an explosion (which is what we saw at the beginning).