Exactly. My oldest son, now 10, has been perfectly able to swim on his own. We live in a former port area with lots of great swimming spots that he visits with his friends. But he's got his swimming diplomas (two of them, which I consider the minimum for this situation).

Sea, though, can be tricky. Half a mile out to sea, currents can be very different. I know that I as a kid once floated on a tiny inflatable boat quite a bit out to sea, and my dad swam after me to drag me back. I thought I could get back on my own, but my dad clearly wasn't entirely convinced.