I will try until the experts can give us their expertise.
This puzzle is made up of several stages.
First you have to stop the flow of the water at the ?river? across the harvester. This is complicated and involve the blocking, diverting or stopping flow in 3 or so other places around Serenia.
Once that is done then you can do the round thing-harvester-bathyscape puzzle.
This involves removing more water in the pond where this round thingie is located. This will then expose the stairs you need to do.
From the Coehlo's wt:
There are two levers here for controlling the bathyscaph: one lowers and raises it (the left lever) and the other one opens and closes its door (the right lever).
Begin by pulling it up using the left lever. Close the door on the bathyscaph by using the right lever and then lower it.
Still with the door closed, lift it up. This will cause some over flow and grant you access to the
Approach the well and climb down. Once inside, climb down once more.
Hope that will get you going a bit.