They should do it somewhere shallow first, next to a large city surrounded by water where the land values are high. Requiring a boat for access would make it less feasible, so perhaps just a stairway and/or an elevator at the water’s edge instead. Put it just deep enough that it’s not visually distracting to passers–by, and shallow enough that the residents can still see the sun through skylights.
The renders with tropical ocean life right outside the windows are a fantasy; most of the sea bottom is undifferentiated mud.
Of course you could just build a marina and let people live in houseboats. You’d get the same population density with fewer of the problems and lower costs.
Biosphere II is worth a visit. They're still running it as a non-isolated research station. The original had several very specific problems (trees need wind to form strong roots, fresh concrete absorbs a lot of oxygen, their crops besides sweet potatos had serious soil nutrient problems, which meant they spent almost all their time desperately subsistence farming). Based on what they did we could run a Biosphere III today pretty well, which means I would call the Biosphere II experiment successful.
It went pretty well. A small amount of extra oxygen needed once during the 2-year period. Ecosystems that shifted in unexpected ways but did not collapse. 100% sealed and self-sustaining is going to be very hard, but 98% is much easier and good enough for many purposes.
Yes, they failed every single one of their objectives, within weeks. They failed the psychological ones even harder than the others. (Whoever keeps pushing at a colony on Mars, should look at those later ones.)
But the GP also has a good point. They failed due to overambition more than to lack of results.
Getting people to live a month in a well-known but extremely harsh environment?
There's actually way fewer things that could go wrong than on the Biosphere experiment. Time exponentiates every failure mode, shorter times fix lots of things.
It may still be overambitious, we will only know after they try, but it's less ambitious than the other one.
We should give that another go. Unless humanity can build and operate BioSphere 3 as an unqualified success, we are nowhere near ready for a settlement on Mars.
However, it hasn't been operated as a long-duration closed-cycle ecosystem since 1994. It's surprising to me that lots of people talk about bases on the Moon and Mars, but basic fundamentals like this are neglected.
Biosphere was an attempt at a sealed ecosystem. It's not at all comparable to a building designed as living quarters for people who come and go as they please.
This is kind of what I feel about McMurdo Station. Why put it so far away? Put it near a Vail resort. Lots of snow. Same with the ISS. Kind of useless that far away. Treehouses are so much cheaper.
The renders with tropical ocean life right outside the windows are a fantasy; most of the sea bottom is undifferentiated mud.
Of course you could just build a marina and let people live in houseboats. You’d get the same population density with fewer of the problems and lower costs.