I’d say the butterfly is the most energy intensive way to swim, and dead man’s float is the least energy intense.

Swimming is the best exercise you’ll ever do, and you should be able to do it for most of your life. You can do it to get ripped, you can do it to rehab.

The 2 most important things when swimming are: don’t get overconfident, and don’t mess around with safety. The ocean absolutely doesn’t care about you, and it’s amazing how little it’ll take to become disoriented. Never swim halfway past where you can’t see the shore, and never swim more than halfway past the longest you’ve swam before.

Saltwater is generally fine if there are no nasty organisms in your neighborhood, but fresh water swimming can kill you if the water is stagnant or polluted.

If you’re looking to swim for exercise or fitness my biggest recommendation (after goggles) is get yourself a speedo/teva suit (if you don’t want a banana hammock get the thigh length shorts), you’ll be amazed how much further you move per stroke and how much less energy it takes to go from a to b.

As I’ve said in another reply, the most efficient stroke with easy breathing is probably the backwards frog, it’s very easy to learn, just pulse like a jelly fish while keeping a bit of your face out of the water.

I’m glad you had a great experience and you’re looking to continue practicing! Knowing even the basics can be life changing.

If you ever find yourself under water and can’t tell which way is up (this can happen surprisingly easy), follow your bubbles, bubbles always go up