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.
Swim Drills Day.
Today we will work on something called the Fist Drill. Swim at least 4 lengths to warm up (100) - you can alternate free style and sidestroke or breast stroke. After you have finished your warm up, you will start your next length with your hands closed in a fist. Swim like this for 4 strokes, and then open your hands for 4 strokes, alternating until you get to the other end. Alternate 25 yds of 'Fist Drill' and freestyle swimming. This should get you to get a better 'feel' for the water.
Keep moving and complete 400 yards or 1/4 of a mile! When you are done swimming, work on stretching your back, your arms, shoulders and neck muscles.