Surface radars don't work too well with objects very close to the sea. It becomes hard to pick them out from the clutter caused by reflections especially if the

Surface radars don't work too well with objects very close to the sea. It becomes hard to pick them out from the clutter caused by reflections especially if their size is comparable to the height of waves. That's why floating stray shipping containers are so dangerous to small boats and why sea skimming missiles are so effective.