Here's why:
* Osmoregulation: Sharks maintain a specific salt balance in their bodies. They have adaptations that allow them to regulate their internal salt levels in saltwater environments. However, in freshwater, they would constantly be taking in water through osmosis, leading to a dangerous imbalance and potentially death.
* Physiological Adaptations: Tiger sharks, like other marine sharks, have specific adaptations for breathing and osmoregulation in saltwater. These adaptations are not suited for freshwater environments.
While they might be able to briefly enter freshwater areas with a high salinity, prolonged exposure to pure freshwater is fatal for tiger sharks.