Frogs are in danger more from water loss than absorbing
Frogs don't often drink with their mouths, they absorb
water through their skin. They have a 'seat pouch',
an area on their bellies which is designed for water
absorbtion. They absorb through capillary action from
water or a moist surface.
Frogs also control water by burrowing and cocoons of
shedded skin if in dry conditions.
They can also change the colour of their skin, which
changes how much heat they absorb. Bright green is more
absorbant then darker greens or browns.