Thank you everyone for your thoughtful suggestions.
I've been looking further into all of these ideas, and come up with some interesting possibilities.
I'd just like to clarify one point brought up...
One requirement I have is the shoe must be sturdy with a robust sole.
There is a reason this is especially important to me.
I was witness to a diver in full gear taking a very bad fall on a slippery dock. Fortunately, and somewhat miraculously, the diver was not hurt, but it left me profoundly worried about falling myself. Since that time I have avoided thin flexible dive booties. Now I always opt for expedition weight dive boots with flat sturdy soles, which I replace at the first sign of wear.
I'm looking for similar characteristics in a dual purpose dive boot/street shoe.
And yes, I realize I may be over-thinking this, but that's the nature of obsession...
which in my case is to travel and dive safely with the absolute lightest and most minimalist gear possible.
Thanks again,
K.