What does it mean that only 5% of the ocean floor is “mapped” and why is that number so small?

Question

I often see this statistic referenced, but I don’t understand exactly what it means. And why only 5 percent? Is it because of the ocean’s unfathomably massive size? The cost of mapping? It’s not worth mapping? All of the above?

In: Earth Science

Answer 1

All the above. Oceans account for far more of the world’s surface than land, and their sheer vastness and isolation makes it prohibitively expensive to map them with very little tangible benefit.