Once you learned to swim, even though you haven't swam no matter how long, you still know how to swim when in the water.
You learned a foreign language, you haven't used for a while, you will lose it.
It's muscle memory is better than brain memory.
Didn't muscle memory depend on the brain too?
Who wants to explain it?
Steve panicked while we were snorkeling in Mexico a few years ago because he didn't know how to swim. After we got home, he signed up for swimming classes and has continued since then.
This time he signed up for a class on Saturdays at the community college near our house, and he can bring a guest to swim during the open sessions on Wednesdays and Thursdays. I have gone with him a few times. This one is six lanes x 75 feet pool.
I learned swimming when in high school. Even though I haven't swam often the past few years but I still know how to swim, thanks to muscle memory.
I always swim non-stop for 20-30 mins, then get out. I don't like soaking in the water too long, because the pool chemicals smell bad and make my hair stiff.