The buff you receive from using this hook used to be limited in how close to the surface of the water you could get. Before patch 2.4 skimming the surface was impossible, your camera had to be under water, and thus your character under water. However, since patch 2.4 I've been able to sit right on the surface of the water and not lose the buff. It only drops if my character leaves the water (jumping, running up the shore).
Quite convenient as now it's easier to control my character and see where I'm going.