Here's why:
* Water retention: Cactus plants have evolved to thrive in extremely arid environments, where water is scarce. Their thick, fleshy stems store water, and their spines help minimize water loss through transpiration.
* Root systems: Cactus roots are shallow and spread out, designed to quickly absorb any available water from rainfall. Underwater, their roots would be unable to function properly and the plant would likely rot.
* Photosynthesis: Cactus plants need sunlight for photosynthesis. Underwater, they would lack sufficient sunlight to produce energy.
In summary: Cactus plants are uniquely adapted to survive in desert environments and would not be able to survive underwater.
