It's not uncommon to find uncharted reefs
. Cruisers usually avoid sailing through this area because it is too risky with uncharted reefs
just below the surface. Occasionally a new volcanic island forms in the same area. Rarely in the uncharted expanses of the southern oceans, unfortunate sailors have lost
their yacht on an uncharted reef.
Some nautical charts
display the lines along which soundings were taken in the construction of depth
contours. When I sailed from New Zealand
, the chart showed that most of the seabed was not sounded in the construction of the chart.
Now that we have satellites surveying the oceans, I suspect that the government
knows of even the tiniest pieces of oceanic real estate.