A great dry land exercise to help swimmers understand and feel the movement pattern for freestyle arm recovery. A fixed stable surface allows the swimmer to move through the arm trajectory, and focus on key elements for example width, elbow lead, maintaining forward momentum, high elbow (without lifting), and arrival at correct entry position.

Many swimmers we coach, come to us feeling they need to lift the arm up, and over the water, essentially against gravity, which results in over rotation and general torso instability. They may have been taught come kind of 'high elbow' concept, where the elbow is hitched up too high, causing impingement issues in the shoulder and limited the ball and socket joint 'ROM' (range of motion)

One of the aims we encourage in freestyle, is to capture as much forward momentum from the recovery arm as possible. Because inertia serves us better when travelling continuously without stopping or changing direction. Maintaining body balance is also encourage, hence moving your arm FORWARDS, not back or upwards will attain these outcomes.
When you try this Feel the ease of movement in the ball and socket joint in the shoulder, as the arm maintains movement in the same plane, limiting pain and injurious movements.

Worth noting in this demo style swim that is slow, the arm gently travels back in a long stroke to the direction of the quad. Slow tempo/ low cadence needs longer slower strokes. If the swimmer speeds tempo, the catch would be shorter, not travelling back as far as the leg.