Underwater Swim

Under Water Swim Stroke - breakdown.

Kick off the wall

Repeat - double arm pull, GLIDE - kick and recover - GLIDE

Kick can either be a scissor kick or a breast stroke kick BUT when swimming with fins you need to learn scissor / flutterkicks.

Kick hard / pull hard = glide fast.

Related article: The Challenges of Passing Military Swimming Tests

You don't have to be a competitive swimmer to ace Spec Ops Training, you just need to be good and comfortable in the water.