I am working on a seastead design.
The seastead will have 4 foot wide columns that go 13 feet into the water at
a 45 degree angle going out from the corners of a 40 foot by 40 foot platform, which is above the water,
with cables from the bottom of the columns to the adjacent corners.
The seastead is about 30,000 lbs I think but this is NOT a normal boat hull shape,
it is more like a tiny oil platform as far as drag.


The seastead will be solar powered and we just want to use that electricity for propulsion.
Given our high drag and limited electricity we are looking for large slow propeller designs.

The submersible mixers look like they might work.  For example perhaps this one:


Japanese
      https://www.shinmaywa.co.jp/english/products/pump/introduction/sm_sme/sm-vrtn.html
      https://www.mrm-shinmaywa.com/filesdirectserver/itp1/z_itp_12042022f9ii/originalz-z721968334010.pdf
          propeller: 2.5 meters 
          thrust: 3200 newtons   (720 lbs)
          Is stainless and ok for seawater
          2–3.2 kW


The rating of 3200 newtons at 3.2 kw is for thrust in stationary water. 
The question I would like you to investigate is once the water is moving 
how much thrust does it have and how much power draw will there be.
I expect thrust drops as vessel speed increases, and power draw should drop as well.
Please fill out this table with your best estimates:

  MPH         Thrust     Kw
  0           3200       3.2
 0.5
  1
 1.5