Auditory functioning is incredibly intricate, making vision seem simple by comparison.
By the Whiskers
Using their facial whiskers, harbor seals can sense the size and shape of an object by the wake it makes in the water. They can discern a difference as small as 2.8 cm.
A seal can detect different species of fish by the wake they create, as well as size, letting a seal selectively pursue promising prey.
Other marine mammals with facial whiskers, including otters and sea lions, have whisker sight; an exceedingly useful sense for fishing in murky or low-light water. Or is that whisker hearing?