Regarding the Mokulua Islands...a kid named Billy Weaver was killed in 1958 while playing with friends on an air mattress between the islands. They got him to the island and went for help but he lost too much blood before help arrived.
I grew up in Kaneohe and my buddies and I would swim out to the Mokuluas on beautiful flat winter (kona wind) days just like the one pictured. It really wasn't spooky until you got to the deep water right at the islands and started thinking about Billy Weaver. I think we tended to swim a little closer together at that point.
As for fatal attacks since 1958, there have been many. According to Wikipedia's "List of fatal, unprovoked shark attacks in the United States by decade" there were six in Hawaii in the 1990's alone.