There are 5 parts to a dragon boat stroke: reach, catch, pull, exit and recovery.
REACH - this is the full extension forward. You should aim your paddle at the mid thigh of the person in front of you, drop your outside shoulder and rotate from the waist (see picture).
CATCH - This is when the paddle hits the water. The paddle should be put into the water with purpose rather than dropped in, use the top arm to drive the paddle into the water, your hand may get wet.
PULL - Use your bottom arm to pull the paddle through the water. The paddle should be at 90 degrees to the boat and stay as vertical as possible. Rotate your body so you are back in an upright position.
EXIT - Use your top arm to pull the paddle out the water, keep the paddle as vertical as possible as any scooping is a waste of energy.
RECOVERY - Return to the reach position to prepare for the next stroke.