Do it for posture, strength, and pain relief
Squats, deadlifts, and pull-ups are great exercises to strengthen the entire backside of the body (posterior chain), but these movements also require a close attention to form and technique. This variation is extremely effective (you'll feel it from head to toe) and great for all levels of fitness: The Prone Swimmer.
As I SIT here and type this, I am like most humans in society today. We slouch, sit, and stare at our phones more than we think we do. In turn, we have developed an anterior (front) chain-dominant body. If you couple this with more anterior focused exercises, you run the risk of injury and posture issues.
An effective way to combat this problem is to pull twice as much as you push. For every one pushup/shoulder press, do two pull-ups/rows.
This Prone Swimmer exercise is great because it targets the whole posterior chain, fixes imbalances, and can be done from anywhere with little to no equipment.
Lie face down with your legs and arms extended.
Grab a light weight/no weight (in this case I am using a backpack) and pick it up off the ground.
Keeping your arms extended the whole time begin to march your legs. Try to prevent your body from rocking side to side as you switch legs.
Aim for 5 per side.