In my opinion the Combat Side Stroke is by far the most efficient style of swimming. Fun fact I can also swim just as fast with the side

My first short video demonstrates the combat swimmer stroke!

Augustana Swimming & Diving Costa Rica Blog - Augustana University Athletics

Learn 8 different swimming strokes and styles – Ninja Shark Australia

Who needs a sidestroke? A story of a forgotten stroke • Swimmo

3 Reasons Not to Practice Holding Your Breath for Underwater Swims

Three Things That Slow Your Swim Time – Stew Smith Fitness

Learn the Combat Sidestroke and Swim Like a SEAL

Introduction to the Combat Side Stroke - CSS

Ask Stew: When Should I Practice Swim Strokes on Different Sides?

How to Prepare for Running and Swimming on the PST

Learn the step by step process required to master the Combat Sidestroke with Fins from basic drills to the full stroke and alternative strokes.

The Combat Sidestroke with Fins

How to Swim Side-Stroke

Why is the sidestroke not done in competitive swimming? - Quora