"Dave Doe" wrote in message .

Water weighs the same above or below the waterline, and the
same in or
out of water assuming the same gravitational potential.

No it doesn't!

The *mass* is the same.

Take a plastic bag of water and push if off a bench.

Take the same and do the same off a wee bench in a tub of
water.



Dave, the water in a ballast tank is KNOT IN the water.

Sheesh!!!!