I love the fact that I learn so much from home educating my children. Did you know that freighters can carry a grater cargo load by salt water than by fresh? Salt increases the vessel's buoyancy. The
plimsoll lines are the marknings for the ship's hull: when you've loaded it this far into the water, stop: deeper/more cargo could sink the ship.
Today we experimented with cargo loads for different kind of ships (tin foil, foam meat tray, egg carton, dixie cup). We also charted plimsoll lines for fresh water vs. salt water. So cool. I learn something new every day. Literally.