Deltoid Muscle Stretch in the Pool
Deltoid is the largest and the most powerful muscle of the shoulder girdle. It is the most active muscle in arm movements which also makes it prone to injuries. In order to keep your deltoid muscle healthy, always stretch it properly when exercising.
Put your right arm across your chest as far as you can. Using your left hand, push your right elbow into your chest until you feel your deltoid expanding. Hold that position for 10 - 15 seconds then repeat on the other side. Do not move your elbow during this exercise. Your breathing should be deep and relaxed. Below is the video demonstrating this stretching exercise: