What about other bodies of water than the ocean? Like lakes or somerhing. Mostly still water.

Or where I live, they have put swimming lanes in the ocean. Like a dock that extends out on two places, and with lane separators in between. Free and safe.

But what I did was to just pay for a swimming course over X weeks. That included entrance to the swimming facilities on the course days. Find one for your level, and the progress will be swift.