The eyes of pinnipeds are relatively large for their size and are positioned near the front of the head.
One exception is the walrus, whose smaller eyes are located on the sides of its head.
This is because it feeds on immobile bottom dwelling mollusks and hence does not need acute vision.
A seal's eye is adapted for seeing both underwater and in air.
The lens is mostly spherical, and much of the retina is equidistant from the lens center.
The cornea has a flattened center where refraction is nearly equal in both water and air.
Pinnipeds also have very muscular and vascularized irises.
The well-developed dilator muscle gives the animals a great range in pupil dilation.
When contracted, the pupil is typically pear-shaped, although the bearded seal's is more diagonal.
In species that live in shallow water, such as harbor seals and California sea lions, dilation varies little, while the deep-diving elephant seals have much greater variation.

On land, pinnipeds are near-sighted in dim light.
This is reduced in bright light, as the retracted pupil reduces the lens and cornea's ability to bend light.
They also have a well-developed tapetum lucidum, a reflecting layer that increases sensitivity by reflecting light back through the rods.
This helps them see in low-light conditions.
Ice-living seals like the harp seal have corneas that can tolerate high levels of ultraviolet radiation typical of bright, snowy environments.
As such, they do not suffer snow blindness.
Pinnipeds appear to have limited color vision, as they lack S-cones.
Flexible eye movement has been documented in seals.
The extraocular muscles of the walrus are well developed.
This and its lack of orbital roof allow it to protrude its eyes and see in both frontal and dorsal directions.
Seals release large amounts of mucus to protect their eyes.
The corneal epithelium is keratinized and the sclera is thick enough to withstand the pressures of diving.
As in many mammals and birds, pinnipeds possess nictitating membranes.

The pinniped ear is adapted for hearing underwater, where it can hear sound frequencies at up to 70,000 Hz.
In air, hearing is somewhat reduced in pinnipeds compared to many terrestrial mammals.
While they are capable of hearing a wide range of frequencies (e.g. 500 to 32,000 Hz in the northern fur seal, compared to 20 to 20,000 Hz in humans), their airborne hearing sensitivity is weaker overall.
One study of three species—the harbor seal, California sea lion and northern elephant seal—found that the sea lion was best adapted for airborne hearing, the harbor seal was equally capable of hearing in air and water, and the elephant seal was better adapted for underwater hearing.
Although pinnipeds have a fairly good sense of smell on land, it is useless underwater as their nostrils are closed.

Pinnipeds have well-developed tactile senses.
Their mystacial vibrissae have ten times the innervation of terrestrial mammals, allowing them to effectively detect vibrations in the water.
These vibrations are generated, for example, when a fish swims through water.
Detecting vibrations is useful when the animals are foraging and may add to or even replace vision, particularly in darkness.
Harbor seals have been observed following varying paths of another seal that swam ahead several minutes before, similar to a dog following a scent trail, and even to discriminate the species and the size of the fish responsible for the trail.
 Blind ringed seals have even been observed successfully hunting on their own in Lake Saimaa, likely relying on their vibrissae to gain sensory information and catch prey.

Unlike terrestrial mammals, such as rodents, pinnipeds do not move their vibrissae over an object when examining it but instead extend their moveable whiskers and keep them in the same position.
By holding their vibrissae steady, pinnipeds are able to maximize their detection ability.
The vibrissae of phocids are undulated and wavy while otariid and walrus vibrissae are smooth.
Research is ongoing to determine the function, if any, of these shapes on detection ability.
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The eyes of pinnipeds are relatively large for their size and are positioned near the front of the head. One exception is the walrus, whose smaller eyes are located on the sides of its head. This is because it feeds on immobile bottom dwelling mollusks and hence does not need acute vision. A seal's eye is adapted for seeing both underwater and in air. The lens is mostly spherical, and much of the retina is equidistant from the lens center. The cornea has a flattened center where refraction is nearly equal in both water and air. Pinnipeds also have very muscular and vascularized irises. The well-developed dilator muscle gives the animals a great range in pupil dilation. When contracted, the pupil is typically pear-shaped, although the bearded seal's is more diagonal. In species that live in shallow water, such as harbor seals and California sea lions, dilation varies little, while the deep-diving elephant seals have much greater variation.
On land, pinnipeds are near-sighted in dim light. This is reduced in bright light, as the retracted pupil reduces the lens and cornea's ability to bend light. They also have a well-developed tapetum lucidum, a reflecting layer that increases sensitivity by reflecting light back through the rods. This helps them see in low-light conditions. Ice-living seals like the harp seal have corneas that can tolerate high levels of ultraviolet radiation typical of bright, snowy environments. As such, they do not suffer snow blindness. Pinnipeds appear to have limited color vision, as they lack S-cones. Flexible eye movement has been documented in seals. The extraocular muscles of the walrus are well developed. This and its lack of orbital roof allow it to protrude its eyes and see in both frontal and dorsal directions. Seals release large amounts of mucus to protect their eyes. The corneal epithelium is keratinized and the sclera is thick enough to withstand the pressures of diving. As in many mammals and birds, pinnipeds possess nictitating membranes.
The pinniped ear is adapted for hearing underwater, where it can hear sound frequencies at up to 70,000 Hz. In air, hearing is somewhat reduced in pinnipeds compared to many terrestrial mammals. While they are capable of hearing a wide range of frequencies (e.g. 500 to 32,000 Hz in the northern fur seal, compared to 20 to 20,000 Hz in humans), their airborne hearing sensitivity is weaker overall. One study of three species—the harbor seal, California sea lion and northern elephant seal—found that the sea lion was best adapted for airborne hearing, the harbor seal was equally capable of hearing in air and water, and the elephant seal was better adapted for underwater hearing. Although pinnipeds have a fairly good sense of smell on land, it is useless underwater as their nostrils are closed.
Pinnipeds have well-developed tactile senses. Their mystacial vibrissae have ten times the innervation of terrestrial mammals, allowing them to effectively detect vibrations in the water. These vibrations are generated, for example, when a fish swims through water. Detecting vibrations is useful when the animals are foraging and may add to or even replace vision, particularly in darkness. Harbor seals have been observed following varying paths of another seal that swam ahead several minutes before, similar to a dog following a scent trail, and even to discriminate the species and the size of the fish responsible for the trail.  Blind ringed seals have even been observed successfully hunting on their own in Lake Saimaa, likely relying on their vibrissae to gain sensory information and catch prey.
Unlike terrestrial mammals, such as rodents, pinnipeds do not move their vibrissae over an object when examining it but instead extend their moveable whiskers and keep them in the same position. By holding their vibrissae steady, pinnipeds are able to maximize their detection ability. The vibrissae of phocids are undulated and wavy while otariid and walrus vibrissae are smooth. Research is ongoing to determine the function, if any, of these shapes on detection ability. The 
Pinniped