The Hawaiian monk seal has a very short coat that is usually brown to gray in color and turns black when it is wet. The under side of the seal is kind of a cream color and the color extends to the nose of the seal. Seals have two layers to their fur; the outer layer and the inner layer. The outer layer of fur keeps the inner layer dry and warm, so the seal doesn't get cold. The vibrissae, or whiskers, are used to hunt when the seal is in poor visual conditions. The whiskers allow them to feel slight movements in the water, which makes it easier to find a swimming fishes trail. The hind and fore flippers aid with swimming in water and walking around on land.

The monk seal mandible, which is part of the axial skeleton, over time under went a transition during their evolution. The mandible helps the seal consume food from suction-feeding or grip-and-tear feeding. Depending on the size of the prey will determine whether the monk seal will use a biting method or a sucking method. The mandible is required for the survival of the species since it aids in food consumption. The phalanges, which are part of the appendicular skeleton, are present in both the hind and the fore flippers and assist with swimming in the ocean.

Hawaiian monk seal respiratory system consists of the nose, mouth, pharynx, larynx, trachea, bronchi, and lungs. Since they are able to breath on land, seals do not have gills to breath under water, so in order to be under the water for long periods of time they absorb oxygen through their blood. To do this they breath all the air out of their lungs before they dive into the water. Their respiratory system works by breathing air in through their nose, witch goes down their windpipe, and into their lungs. They then breath out through the same organ and excrete carbon dioxide.

The main parts of the circulatory system in seals are the heart, veins, and arteries. The circulatory system in seals works very similarly to that of us humans. The heart pumps blood to the lungs so it can get oxygenated, and then the oxygenated blood is pumped to the rest of the body through arteries. The veins in the body are responsible for carrying oxygen-poor blood back to the heart so the process can begin again. The blood is in charge of making sure the seal stays oxygenated while diving in the water since it cannot breath water, and the way it does that is by having the arteries squeeze shut. This limits the blood flow throughout the body, so the seals can absorb the oxygen. While under the water, seals have a higher pain tolerance sice there is limited blood flow.