Mangrove Roots are plants for you to plant land plants underwater or on water. You can also plant it on the water part of the Hill Levels to plant aquatic plants, but strangely... It also slows the zombies that are eating it's bite rate. Even though it is recommended on water, it can also be planted on land and unplantable surfaces, like dirt or road. It also prevents the Bungee Zombies from taking it away since it is really rooted to the ground.