On 15-Jun-2005, Peter wrote:

When two variables are correlated it means that they have
a tendency to vary in the same manner, not that there is a one-to-one
correspondence in each particular case.

Fine - I'm using the term correctly. When you compare kayaks,
you will see that some have overhanging stem and/or stern, others have
plumb stem and/or stern while others still have raked ends. Thus, you
can find kayaks of the same overall length with very different waterline
lengths. It is not automatically true that if a kayak has a longer
overall length it necessarily has a longer waterline length. This is
especially true when comparing kayaks of roughly the same length. That
is why you cannot use overall length as a determining factor in estimating
speed or resistance - only waterline length plays any role.

What is so hard to understand in that?

Mike