This creates a lossy ground that gets rid of stray RF by converting it to heat. You could, but much of your power may end up as heat. When working against any poor ground, much of your signal is lost as heat. I just heard a DX station using a trap vertical at a beach- front location. I used a vertical too, but my signal wasn't nearly as good on his end.
Sand saturated by salt water is a terrific ground plane for verticals.
The ideal ground plane for HF verticals should extend for hundreds, if not thousands, of feet around the antenna. Some hams try placing copper screens under their verticals, but it doesn't offer much improvement. Unless you can move to a tropical island or seaside resort, you can only work with what you have available. The easiest way to reduce the SWR is by increasing the losses, either by putting a resistor or using lossy matching techniques. The acceptability of these techniques is subject to much debate and we don't have space to cover it here.