Complex sentence: This can cause the boom to swing across the deck with great force, injuring anyone standing in the path of the boom, the mainsheet or its tackle as they sweep across the boat.
Split into simpler sentences: This can cause the boom to swing across the deck with a great deal of force. The sudden movement of the boom can cause of severe injury to anyone standing in the path of the boom, the mainsheet or its tackle as they sweep across the boat.