Trunk problem. Water collects beneath the trunk lid. When the trunk is opened water drains into the trunk instead of off to the sides wetting my belongins. I've never had this happen with a new car before. What's the problem?

Hunting water leaks is a pain in the tailbone job to do. I'm assuming yours has the jack in the floor of the trunk, under the carpet.
The spare wheel well is the lowest point in the trunk so the water will collect there regardless of where the leak is. Start with the simplest tools, a flash light and the palm of your hand.
How much water is collecting and how fast does it fill up? Rain water coming up through the floor is unlikely unless the floor is damaged.
First take everything out of the trunk that wasn't in there when it came out of the factory. Take a really good look at the carpet and trunk side liners. Use the palm of your hand and feel the floor carpet for wetness. Your feeling to see if it is wet in a particular area. Using the flashlight look for darker patches as carpets often darken in color when wet. Move to the rear of the trunk and feel the liner on the back of the rear seats. Next run your hand over the side panels where the wheel arches are. This will give you clues as to where the leak is possibly coming from.
If the whole trunk carpet and liners are bone dry the leak is from under the car.
All the doors, the trunk lid and the sun roof are fitted with rubber seals to stop rain and road splashes getting inside the vehicle. Over time these perish and start to leak. Run your hand around the underside of the rubber seal the trunk lid sits on when closed. This is the most obvious place it will leak from. You can do this on each door as well because water can travel a large distance before it finds somewhere to create a puddle. A Sunroof can also leak but they tend to cause puddles in the foot well.
If you get a few dry days you can test for leaks with a hose pipe. Keep the trunk closed and make sure the inside of it is totally dry. Remove any spray nozzle from the hose so it flows at regular pressure. Carefully aim the water so it only flows over the trunk lid. Let it flow for a minute or two trying not to soak the doors at the same time. Turn off the water and leave the car alone for about 10 minutes. Wipe off any excess water on the trunk lid, open it and see if its now wet inside the trunk. Yes? the trunk seal is leaking. You can use this method for the doors and sun roof as well. Door and trunk seals are usually just a 'Push on/Pull off' fit so you can easily change them yourself.

The tail light has a leak in it someplace. it fill up and then drains, check the gaskets carefully and look to see if any drain holes are plugged

Usually the leak is from a faulty gasket, or the lid is not adjusted correctly to seal against the gasket.

Its not designed to drain.
You are probably getting water into the trunk from the trunk lid gasket or one of the tail lights.

check the seal that goes around the lip of the boot also your drains might be blocked

Here is the best way to find out where the water is coming in. Get inside the trunk and have someone you trust close the trunk. make sure you do it when it is daylight or a well lit garage. while you are in the trunk with the lid closed you will be able to see light where there is any gap around the trunk seal and that will be where the water is coming in. some times the sides of the trunk opening gets bent down causing the trunk gasket not to seal properly.

I can tell you why....because it does this in my stratus!!!!

The trunk lid hinges are letting water into your trunk. All the water pools up in and under the spare, the trunk carpet is wet.....more than likely the driver's side of the trunk....pull that trunk carpet back from where that trunk hinge is mounted to the body, reach under there and feel all the water dripping in!

The fix? Unbolt those hinges and put silicone sealant around those bolts and mounts.....that'll take care of that crummy leak.....DODGES!!!!!

Sounds to me like your issue is with condensation from your air conditioner. The condensation isn't properly draining, probably from a damaged or clogged drain hose.

Check for defective spot welds around the plastic inserts on the left and right sides of the trunk. If the spot welds burnt through the metal, there will be holes were water can get in. Use some JB Marine Weld to seal up any holes or cracks in the sheet metal. Also, check the rubber drain holes under those inserts, that are in the sheet metal of the car, to make sure they are not blocked with road dirt. Also, check the weather stripping on the outside of the car, adjacent to the trunk. If the rubber and chrome trim weather stripping is pulling out (on the exterior of the rear quarter panel), then water will leak through the little plastic attaching screws and into the trunk beneath the plastic containers on the left and right front sides of the trunk.