In the Hawaiian stroke, the paddle blade is thrust far forward and fully into the water. However, depending on your arm and body strength, you should stick the blade 100 per cent (strong racers) or 75 per cent (medium-strength racers, e.g. Connor or women) into the water during the catch (penetration phase).
You can download the complete report on SUP race paddling technique as a PDF below.
De Zwart: "When sprinting, my fingers grip tightly around the knob and the shaft so that I don't lose the paddle under any circumstances. Over long distances, however, the fingers must remain relaxed when paddling. Keeping the thumbs loose (as in the picture) allows the forearm muscle to relax. The force is distributed more over the upper body."