Get your swim stroke down first. That will be key. It's just like squating or running, you need to find perfect form and make it a habit. Check out
Total Immersion - it's a great swimming instructional.
I take a lot of rest - my body needs it. But a rest day for me might include a 20 - 30 minute run, or a really easy 30 minute swim, so I just lighten the load while keeping active. I can't sit around for a full day without doing something. I get really annoying and fidgety.
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