Hello,
There is water in the trunk of my 1983 300D Mercedes, and behind the passenger seat.
This happened before, and my mechanic said he got under the car and there
is a drain??...I did A search and found this advice....Still confusing to a novice. Would the direction pertain to the Trunk cover in the back of the Car or theCover in the front. It would be great if I could do this myself and save money and a trip to the mechanic...Here are the excellent directions for this..Anything to clarify is useful advice. Thanks!

"Here's the cure for flooding:

Open the hood and look for some little dimple openings at the rear of the hood hinge pocket. There is a vertical piece of sheet metal in the middle of this area and there is a little opening at the bottom of this vertical piece of metal that also must be clear. The dimple at the rear allows for a drain between the fenderwell and the firewall.

In addition to those two dimples at the firewall and the two in the vertical pieces of metal, there are some drains underneath the master cylinder and the battery box.
I must warn you that cleaning these drains requires very skilled use of a highly sophisticated tool. This tool is a piece of baling wire (for city folks I'm quite sure that an old coat hanger will provide an adequate substitute for baling wire.) Using your sophisticated, high tech tool clean all six of these drain areas thoroughly.
I know it sounds nuts, but it worked for me."