Okay it's behaving properly now ! I was subtracting while you were multiplying the fluid mass density

For the time being I'm using the coefficient of the Pac-car II that is in https://en.wikipedia.org/wiki/Drag_coefficient ... unless I properly understand these 2 pages you've sent (hopefully soon). I understand the 'reference area' concept but I still need to compute it for my ship model.

The ship handling is effectively different now !

And what about angular drag, should the same formula be applied to it as well ? (I've left mine to 5.0f otherwise it never stops turning)

Also, regarding the soft constraint you were talking about, there is a spring joint which I've tried in Unity and while it roughly does the same task I couldn't find a way to move the anchor point in the track. So I had some 'free movement' but I was stuck to a certain position in the track. There is also a configurable joint that might do the job but it's way more complex so not for today ...

thanks