salt water on a lake definetly faster, my local lake is twice as salty as the sea and way faster than fresh, actually its been the fastest lake around the last few summers, allows you to sail much smaller volume boards easier.

have a spot lined up for later that is 7 times saltier than the sea has a wicked sand spit at the perfect angle for our prevailing summer wind, sailed there in the late 80's but on some ancint gear then.