[mattmaroon]

It has that density when full of air? What about when it’s full of highly pressurized salt water?

Or, if it’s open to the environment on the way down, how does it evacuate the salt water and how much energy does that take?

Even if all this wasn’t a perpetual motion machine, which it is (the sea water is just part of the machine), wouldn’t it be easier to just float some solar panels to power a pump?

[sikonomial]

The container can be similar to a hydration bladder (Google what it looks like) that is slightly more dense than salt water.

1. At bottom you fill it with fresh water

2. It floats to the surface

3. At the surface you just empty it and remove the fresh water

4. It starts sinking

5. Jump to step 1

[mattmaroon]

Right. You’re glossing over the energy required to fill a bladder at sea depth with enormous pressure on it. That requires a pump and a lot of power, just like pumping it to the top does.