No need to apologize. Have you not heard of bodies being found in containers, trunks, deep freezers, in pieces in suitcases, under floor boards, in crawl spaces, etc.. We talking criminals, murderers, irrational individuals. Remember BTK.
But then no one said Natalee was in a container, I think what was said was Equuasearch had found something that was interesting to them.
Of COURSE I have heard of bodies being put in containers. The point, from the murderer's perspective, is that the body should never been seen again. If the container weighs it down, hides it from view from above, and keeps it under the sea, that's one thing. But if you have an easier option with the sharks...
The container would ensure that the body (or any pieces)did not wash up on shore.