I'm not sure that high school athletes need to take a day off of playing basketball. Their recovery is probably amazing, and a game of ball isn't necessarily very taxing.
A day off is definitely necessary if they're getting sluggish or feeling beat up, or if they're actually training — meaning sprints, distance running, lifting weights, or ...
Seems like too many comments and not enough answers!
You need to do backstroke along with freestyle, because:
Backstroke covers certain muscles a lot better than freestyle, and
Gym can't perfectly replicate backstroke swim time.
If you're going to swim as much as you do, you may as well get comfortable with a second stroke.
Doing different swimming ...
Anatomically the lower and upper abs is the same muscle, the rectus abdominis (the six pack).
A connection exist between the rectus abdominis and the hip flexors.
The hip flexors try to tilt the pelvis forward (anterior) whereas the rectus abdominis try to tilt the pelvis backward (posterior):
"FIGURE 2. The synergistic action of one ...