Yep. Searching underwater is a whole different ball game from searching on land.
- On the surface, unless you're lucky enough to have land in sight, there are no landmarks; just water in all directions. So good luck fixing your search location in the first place.
- Visual lines of sight underwater are limited, and below the light line, you're totally reliant on a limited set of instruments -- artificial light, sonar, maybe MAD. And if the silt kicks up, you're done with visual searching; you won't be able to see the length of your arm in front of you.
- Even when we know latitude and longitude of where the ship went down -- even if we have GPS coordinates -- the search areas are still huge. #1 even our best measurements have tolerances of error, even in the GPS era. #2 most ships don't sink straight down; they "glide" for some distance like a descending airplane. Depending on the ship's course and speed when it sank, currents, angle of descent, depth of water, and so forth, a ship might hit bottom miles away from where it left the surface. There is actually a whole sub-branch of mathematics devoted to underwater search theory dealing with all those factors, which developed in great part thanks to the loss of USS Scorpion. But that's its own story...
Not to mention that the southern Pacific and Indian Oceans are some of the deepest and least explored regions on Earth. Thanks to Cold War submarine warfare research, we know more about what's under the North Pole ice than we do about the ocean within 1000 miles of Australia. Remember that Malaysian flight that went missing down there? I read something from one of the search team scientists that while they still haven't found the plane, they're consoling themselves with the side effects of the search. The loss of life is tragic, but in the process of searching, they've been making advances in hydrographic science. Mapping new territory, testing new gear and ideas, finding several old lost shipwrecks, and other such things.
Be careful what you wish for. I might let you have it.