It just seems to me that of all the products in the bed liner universe the rubber truck bed mats are the best deal by a long ways. For nearly nothing you can get what amounts to a rubber bed liner that fits most trucks. They cost next to nothing too. Here's what you get...
In the case of the liner I got the liner was a Protecta and was a custom fit for my truck. It fits all the little bumps and cut-outs just right. The liner mat has raised ribs on it and a raised border all around the edge. In addition, on the bottom of the liner are all manner of little bumps that keep the liner mostly up off the truck bed in most places. That makes for better drainage and air circulation.
Even if you did get clogged drains under the mat, the pooling of water would be quickly visible, so you could react and not let that go on for long. SInce the liner is easy to get in and out, it's easy to maintain a watch on the condition of the bed at all times, unlike the situation with the plastic drop in bed liners.
The liner mat I have measures about 3/8 inch in thickness and thus weighs in at right at 70 pounds. This is not a lightweight piece of material at all. It's heavy and thick.
These liners are not easy to scratch nor are they easy to cut. So the material is very tough and durable.
You're also getting a mostly non-skid surface with one of these. There is not easy sliding of items on the mat, if that matters.
Effective as protection for the bed floor of a truck, the mats also fit another way it seems to me.
Put one of these cheap mats over a spray in bed liner and you get added shock absorption over the spray coating. What's more, a mat over another liner that costs a lot more, is protection for the more expensive liner. The mat works great as a sacrifice layer over a spray on bed liner or other liner types.
Who wants to add a spray in bed liner coating and then tear it to shreds. Don't do it. Protect the liner with a mat!
The Protecta bed mat is a popular brand as is the TrailFX or the Dee Zee. Since the rubber truck bed mats are mostly custom fit it may be that your truck has not match. If so you can get a universal mat and cut that to fit. These mats are tough and superior protection for just a very little money.
The TrailFX mat is worth a look.