It's in the terminology. LOA is the distance of the solid boat from stem to stern, exclusive of the bowsprit and boomkin. Visualize a real ship, with a big hulking hull and a dinky little bowsprit pointing the way for steering. Here's the way to say it.....
'LOA (Length Over All)' is 32 feet, which gives you a rough idea of how much cargo it can carry..
It has a bowsprit and a boomkin, so the 'Sparred Length' is 39 feet, which is what the dockmaster needs to know
'Waterline length' is 27.5 feet. Maybe you can talk the yard into basing the cost of hauling and bottom paint on this instead of the sparred length. 8^)