I do research on oceanic lidar. The basic problem is that light is absorbed and scattered by water, to a far greater extent than it is by air. Thus, even though

I do research on oceanic lidar. The basic problem is that light is absorbed and scattered by water, to a far greater extent than it is by air. Thus, even though we have no problem seeing through hundreds of kilometres of air, even a kilometre of water is sufficient to filter out nearly all light [0]. In practical terms, this restricts the ability of lidar systems to detect features underwater. As a general rule of thumb, in the very clearest oceanic waters, a lidar has a maximal range resolution of roughly 70 metres. Naturally, this low range becomes further degraded in coastal waters, which are more turbid. Thus, lidar — the best method we have for mapping land — is basically impossible to use outside shallow coastal areas, and we have to rely on more difficult methods such as sonar (about which I don’t know very much at all). If you want to learn more about this stuff, I can highly recommend [1] — a free and remarkably comprehensive reference on ocean optics (which turns out to be a surprisingly large and useful field). [0] https://en.wikipedia.org/wiki/Aphotic_zone https://en.wikipedia.org/wiki/Aphotic_zone [1] https://oceanopticsbook.info/ https://oceanopticsbook.info/