Stretch Cords for Swim Workout
Tip: Use stretch cords to perfect your swim stroke. It is so much easier to work on your form (technique) out of the water rather than in the water.
The gal in this first video does not do a proper EVF stroke. She basically does a straight arm pull with a bend in her elbow.
The second video is about the three (yes, 3, not 1) resistance cords you should probably own. It is not a video about EVF per se.
The third video is really good concerning the use of stretch cords for EVF technique. However, I recommend you bend over more than Coach Troy does so you more realistically mimic the freestyle stroke. When you do your pulls you want your head to be between your biceps (arms), not sticking up in the air the way Coach Troy does. Your arms, head, and straight spine should all be in the same plane the same way they are when you swim properly at the surface of the pool water.