Although I'd always heard that GWS attack from below, I've seen more than one giant sea bass with jaw/tooth marks on their dorsal surfaces suggesting GWS can and do attack from above as well. I still think the advice of heading to the bottom makes sense. In my 45 years of diving Catalina waters, I've only knowingly had a GWS come close once... a 14 ft swam behind me while I was filming giant sea bass buddied up with the artist Wyland.
When I first moved to Catalina, I was quite nervous about GWS. When I saw Jaws, I stopped diving even though I was working in the summer with Jean-Michel Cousteau. Three years later, he saw me suiting up to dive and asked what got me back in the water. I said I saw "Jaws II."