Yes, the designers put the waterline where a boat's loaded balance is best.
If you keep readjusting your waterline due to more equipment
aboard you are not doing yourself any favors as far as performance goes. Cruisers often overload at first and eat their way to the designed waterline.
When I see boats on their moorings and notice that their waterline indicates they are down by the bow or stern I call them to let them know their boat might be flooding (if I know their phone
numbers). Good thing to do each time you look out on your boat is to take note of where the waterline is sitting.