I have just been asked if a boat will float higher in the water if in salt water rather than in fresh, as for example a swimmer in the Red sea floats higher than in the hotel pool, any thoughts please
You need to take the density of the water you are floating in and compare it to salt water (1025), the percentage difference will be the 'fresh water allowance' when applied to your loaded draught (hardly a worthwhile exercise for a yacht). This allows ships to load more cargo in fresh water ports - when they get out to sea they are then floating 'on their marks'.
I've put it a bit simply - but thats the gist of it.