While some view these purchases as risky investments, experts suggest potential, though legally challenging, future uses, ranging from filling the land to developing floating homes.
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In a market where homes routinely sell for millions, the bargain pricing surprised some residents.
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"I think part of it is just the supply and demand. We're not building enough. And lots of people have lots of money to be able to afford these houses," said Linda, a Bay Area resident.
Despite the low cost, the limitations are clear: the lots are submerged.
For some, the idea of purchasing such property seems impractical.
"That's a really stupid idea. Sea levels are rising so I don't know why you'd buy land underwater, but you never know. Someone will figure it out," said Sam Mitchell, a former San Francisco resident who now lives in Atlanta.
Still, some buyers view the properties as speculative investments.
With land in San Francisco scarce, experts say certain investors are willing to take a gamble on unconventional parcels.
Historian Chris Carlsson said parts of San Francisco were once water and later filled in, though he noted that process would be far more difficult today due to legal and environmental barriers.
"It's just not going to happen. I mean really everybody gave up on that a long time ago and really for good reason. We now today enjoy the shoreline. We never could stand here decades past," said Carlsson, who wrote "Hidden San Francisco," a book about the history of San Francisco.
A previous transaction in 2021 involved a realtor who bought underwater lots and envisioned future development there.
More recently, a Netherlands-based architect who specializes in floating structures suggested such properties could still have potential.
"Most of these locations, as long as they're not on open sea, but in this kind of, as in your place, Bay area, or in flood zones, or in rivers, or in canals, lakes, that's absolutely possible to use that as building ground to place floating foundations there and place units on top of it," said Dr. Koen Olthuis, CEO of Waterstudio.
Olthuis said developments like floating homes could provide an alternative approach to housing, though he emphasized that permitting and regulatory approval would likely pose major challenges.
While the future of these underwater lots remains uncertain, their sale highlights both the extremes of San Francisco's real estate market and the creative - and sometimes risky - ideas that come with it.