On "real" sailing vessels, the critcal height is from the water line, up to the highest element of the mast....which sometimes is the radio antenna located there on the top of the nast. It should be specified as exactly what is being measured...you don't want any ambiquity there.
That total height from the water line up is super critical to know...lest you make a very noisy and destructive passage under a fixed (non-opening) bridge.
From the water line down to the bottom of the keel is referred to as the "draft"....or "how much she draws". That too is critical to know so that you do not run aground unexpectedly.
Some masts are mounted (stepped) on the deck, while some others go through the deck and are stepped on the inside of the hull down at the keel. Vessels are categorized by their overall length..."LOA", not their height.
I hope this helps.