The T-shaped grip at the top of a SUP paddle. Your top hand belongs on it — otherwise you're paddling with your arm alone.
The top hand on the T-grip is the detail beginners most often get wrong — and it visibly costs you drive. Only with the top hand above shoulder height on the grip can you press the paddle down from above and bring your trunk and body weight into the stroke. Let it slide down the shaft and you're left with arm work. Two more points: hands sit roughly shoulder- to hip-width apart, and the blade angles forward, away from you — that too gets held backwards constantly. Paddle length for touring runs roughly 15–20 cm above your height, slightly shorter for racing.