Frogs are adapted to a freshwater environment, but for a short while can tolerate a tidal zone that is not completely salty. In order to live in salt water, they would have to be able to either get freshwater from organisms they eat, as whales do, or be able to drink saltwater and eliminate the salt, via gills, as fish do, or via the nasal cavity as seabirds do. They do not have any of these adaptations. Frogs are skin breathers. They can absorb both oxygen and water through their moist skin. However, their skin can also lose water. The thin membrane of their skin allows for the passage of water by osmosis. In a saltwater environment, would be a gradient, or difference in concentration of water between the internal environment of the frog and the seawater. The high concentration (inside the frog's body) of freshwater would move to the lower concentration of freshwater (in the ocean) and the frog would dehydrate and die due to outward osmosis.