Luther or Barth on the Old Adam Swimming away from Baptism?

Here's one from my friend Micah. He asked me if Luther said something like the old Adam is a very good swimmer. Off to Google, and a number of hits come up:

The Old Adam tries again and again to resurface from his drowning. Dr. Martin Luther once said, "The Old Adam is a very good swimmer"…[source]


The old Adam is drowned in baptism, though as Luther observed, "the old Adam is a mighty good swimmer," and keeps popping up. Baptism takes an instant, and requires a lifetime. [source]


Martin Luther said that, even in baptism, the old Adam remains a frightfully good swimmer. However, when faced with satanic assaults, Luther would grab a slate and chalk these words: "I have been baptized." [source]


Or as Martin Luther is reputed to have said, I tried to drown the old Adam in the waters of baptism, but the miserable wretch can swim!" [source]


Martin Luther says somewhere that “I thought that the old Adam drowned in the waters of baptism, but I discovered the miserable wretch can swim.”[source]

These are only a few of many versions of the quote. Now, what's interesting is that a few hits attributed the same sort of thing to Karl Barth:

Karl Barth once made, that even though the old Adam has been drowned in the waters of baptism, the problem of the human condition is that apparently that Old Adam still knows how to swim. [source]


Baptism is supposed to have drowned the old Adam, and a joke that Barth liked to make is, “It turns out the rascal can swim.” [source]


Karl Barth once said that the Old Creature drowns in baptism but is a good underwater swimmer. [source]

Conclusion
Luther used the imagery of the "Old Adam" often. It's possible he may have said something like the quote attributed to him. That I didn't find any sort of documentation is usually a good sign he probably didn't say it. My best guess is the quote isn't from Luther at all, but is rather from Karl Barth: