Extra Thick PVC Anti-Slip Floor Mat Kitchen Bathroom Shower Room Partition Plastic Interlocking Mat Swimming Pool Engineering Project

I checked out a lot of these mats and finally went with this one, and I made the right choice. It's easy to piece together and cut (I used a utility knife). The material is soft rubber, but once it's laid out, it feels really sturdy and doesn't sag. It does a great job of keeping water out. The only thing is it had a bit of a smell at first, but that went away after a few days.