Crocodiles make full use of their senses in finding and catching prey. Scientists believe they have a good sense of smell out of the water, and their eyesight is excellent. With their eyes located on top of their heads, they can swim along nearly submerged and still see around them. Many species hunt at dusk or night, and the pupils of their eyes, like those of cats, appear in bright light as vertical slits, but can be widened at night to admit more light.
But crocodiles cannot adjust their eyes very well to underwater conditions, and when fully submerged they are log-sighted. While underwater, they are believed to use sound to detect their prey. They have the most sophisticated ears of any present-day reptile, with external flaps that can be closed to protect them in the water.
Crocodiles' senses have stood them in good stead - they have been hunting in much the same way for over 200 million years, and have changed little in that time. They have been fortunate in the environment in which they hunt - birds and animals must come to the water to drink, and the rivers have always been stocked with fish.