Run on a flat path, track or treadmill. You can use the 8/2 method of 8 minutes running, 2 minutes walking. RPE should be light - 5/6 out of 10.
Kick/Balance Drills Day. Get in the water and kick with your hands by your side, and your head down for as far as you can. When you need a breath of air, turn your head to the side, but try NOT to pick up your head. Try to kick one length and then swim the next length. Notice how you have more awareness of your kick and your body position in the water.
Focus on pressing your chest into the water on the kick phases and carry this feeling over to the swim portion of the workout.
When you are done swimming, work on stretching your back, your arms, shoulders and neck muscles.