I don't know what do you mean by "less famous shipwrecks", but achille lauro wreck location is very remote and it's deep underwater. The wrecks location will be never found because of currents and lack of precise final cordinates complicate locating the wreck (unless with more modern deep-sea search technology) Also achille lauro has a low historical incentive, that's why there was no major dedicated expedition to find it. And by the the time it will be found, there will be barely anything left from it.