Bacterial and fungal diseases and rot can infect them, and they can die if there’s too much water. Don’t submerge the roots for too long. Here’s a tip: make sure you only water your cactus once a week, and before you even do that, do a stick test. Insert a stick into the soil. If the stick comes out with dry soil, then it is ready for watering. But if not, you will need to wait a while until the soil is dry, or else it can kill the plant.