In my opinion the Combat Side Stroke is by far the most efficient

My Stroke of Insight Summary of Key Ideas and Review

Lower back pain from cycling: How to fix it

Healthy habits help preserve brain health, despite genetics

The 48 Laws of Power — Book Notes, by Si Quan Ong

How to Become a Better Military Rescue Swimmer

Underwater diving - Wikipedia

Why Does the Navy Use the Combat Side Stroke?

Is swimming a good way to build up muscles? - Quora

Tom Wolfe: The Birth of 'The New Journalism

Spec Ops Use of the Combat Swimmer (side) Stroke (CSS) Explained

Fix For Sinking Legs During A Swim

Ask Stew: How to Swim with Cammies

Swim Like a SEAL: How to Do the Combat Side Stroke - Breaking Muscle

Super efficient combat swimmer stroke (css)

Learn 8 Different Swimming Styles, Strokes, & Techniques