Now that's the first time I hear of that method, very interesting. ThanksKey is to keep eye contact and let the GW know that you can see it.
If it approaches you then you MUST swim toward it. It doesn't feel right at the time but the it will make the shark think twice. Don't sprint away splashing and making alot of noise, you'll just create extra interest.
Try stay calm, call for the boat and get out.
GW's are incredibly curious and most often they're just coming to have a look you.