They feel the vibrations
The smell them with their tail
They use a tentacle on their head to detect chemicals emitted from prey
They use ultrasonic to determine the preys exact location and depth
They excrete a thin layer of mucous that traps prey so they can return for it later (similar to a spider)
Algae, Other amphibians and small mammals.
Gills and a membrane behind the ear.
Gills and Skin
Lungs and Gills
An optical opening parallel to the pupil.
Lungs and skin