Crossing over occurs when the swimmer initiates their catch and brings their arm across their body. When the arm crosses the body, it closes the space on the anterior shoulder. The anterior shoulder contains the supraspinatus, the most commonly injured rotator cuff muscles.
Solution: The most common reason for this error is a lack of emphasis on biomechanics. Most swimmers can prevent a crossover catch with concentration and appropriate cuing from their coach. If the swimmer lacks shoulder blade stability, this may be causing them to cross their arm across their body on the catch. Stabilize the shoulder during the initial catch by performing the compact position. In the compact position, it is nearly impossible to cross over and impinge the anterior rotator cuff muscles.
Use a snorkel. Keep your face underwater but tilt your head slightly up to watch what happens after your arms enter the water.
Film a friend. Bring a camera to the pool and ask a friend to film from the pool deck. Swim toward them as they film. Review your clip, make adjustments and film again for confirmation.