Ok .. so here comes the first live simulation.
http://roger.questions.cz/other/sim.zip
Just unzip, read the readme.txt for controls, go to bin, run the exe. It runs in window, it can be resized as you wish, just note that the picture will try to keep aspect from 3:4 to 16:10.
You can control: speed, planes, rudder, tanks and there is also course autopilot.
What is simulated now:
Engine thrust, speed and angle dependent drag. Drag caused by turbulences while surfaced is not simulated.
Dynamic lift - you can try to dive the boat with empty tanks or surface boat with full tanks.
Dynamic stabilization - boat tries to point to where it goes, just try surfacing from deep with zero speed.
Hydrostatic lift, hydrostatic stabilization in pitch axis - visible especially on the surface, ship tries to 'lie on the water'.
Bank axis is fixed for now. If you try to pitch your boat to 90 degrees it will collide with rudder effect and boat will twist in very very weird fashion. Don't do that or your submariners will get sick ! :-D Will be solved later.
Change of weight (flooding tanks) - buoyancy change is constant, does not depend on depth at the moment.
Most effect depends on how much the boat is submerged (drag for example) so even jumping out of the water should be more or less correct (like the boat will eventually fall down).
Only animated part of the boat is the screw now. There is some limit of how fast it rotates because some ugly interferences shows up at the high speeds. We will need some blurred screw model for these high speeds, similar to what flight sims use.
There is no depth limit, no fuel or HP air limit. There is no ground. Water is flat now, no waves or spherical shape.
So take this as a basis, do some tests .. and tell me what do you think about it, especially about the physics.
BTW: I know I was talking about the particles .. there are none at the moment, sorry for that.