Yup. And I had a (minor) epiphany when I realized how I have to learn to breathe before I can focus on anything else. I was using fins, and managed to look back at my hand emerging from the water, and hey presto, I got to the other side without feeling my head was going to explode. Amazing how enough air made it possible to start thinking about hand position and arm position and finicky stuff like that.

Without fins I'm still only half-oxygenated, but working on it.