Depths

Sounding the floor

Depths are the shape of the world under the water, measured one sounding at a time since before anyone wrote it down. We keep that record live.

How we read it

fathom     6 feet, the old unit
soundings  the numbers on the chart
shoal      shallow, and getting shallower
datum      the reference low water

Why they matter

The chart is a map of what you can't see. Trust the soundings over your eyes — the water lies about how deep it is.