“Imagine there’s no countries / It isn’t hard to do / Nothing to kill or die for…”

I know something about islands. My parents still live in a place that launched a thousand postcards (and a million unforgivable muumuus.) Those of us who stay longer than a cruise-ship cycle learn that it’s not all Eden, but it takes a particular talent—enter “two guys with a blog and a love of Ayn Rand”—to combine the tropics’ worst features—isolation, claustrophobia, monotony—with all the charm of an office park.

This latest fever to seize the libertarian imagination offers total freedom … to bob around the ocean in concrete tubes. Each person would have 300 square feet within the shaft, with space for solar panels and satellites on top.

These “seasteads” would hypothetically coalesce into city-states, offering occupants their choice of governments. “If misguided policies arose, citizens could simply motor to a new nation,” co-founder Patri Friedman (grandson of Milton) told Wired. He and his partner Wayne Gramlich have just scored $500,000 from PayPal founder Peter Thiel and plan to build a prototype in San Francisco Bay within two years.

It’s perfectly wonky—which is to say theoretically sublime but lacking any human consideration. People don’t, nor should they, switch national allegiance as easily as sweaters. Places aren’t interchangeable nor culture yet irrelevant. Granted, this is an experiment whose subjects participate by choice, but it’s hard to conceive a crueler exile.

Nothing time tossed or memory endowed. Nothing unique save the variegated mousepads of technocrats who never learned to play well with others. It’s a steep price to pay for freedom: being left alone is one thing; being alone is another.

But it should be fun to watch. From shore—with its open roads and ancient haunts. Ideally, the toll in lost liberty would be less, but I’ve yet to meet anyone who could write a constitution wiser than Mr. Madison’s. Certainly not two bloggers and a billionaire.