Sunning themselves on rocks or waddling  awkwardly across the beach, it’s easy to think of these immobile  mammals less as sea lions, and more as sea house cats. But don’t be fooled by their  beachside behavior. Under the waves, sea lions are  incredible endurance hunters. Hurtling around at speeds from  4 to 18 miles an hour and hunting for up to 30 hours at a time, these majestic mammals live  up to their name. And thanks to a suite of  physical adaptations, finely tuned over millions of years,  they make for resourceful foragers. To find their favorite food, sea lions hunt much deeper than  many of their semi-aquatic peers. With some species diving to  depths of nearly 400 meters, they’re able to cope with  the mounting pressure by collapsing their pliable rib cage,  and compressing a pair of springy lungs. This pushes air up through  the smaller airways, collapsing rings of cartilage as  oxygen travels out from the lungs, to be held in the larger, upper airways. Upon surfacing, this air will be  used to re-inflate the lungs, but for now their heart slows  down to preserve oxygen. Blood flow is redirected towards  only the most essential organs like the heart, lungs, and brain, which rely on reserve oxygen  stored in blood and muscle. Once they arrive at their hunting ground, sea lions depend on their superior  vision to find their prey. Most mammal eyes have  a structure called a lens– a transparent, convex structure whose  shape refracts light to enable sight. In humans, this lens is curved to process  light waves traveling through air. But sea lions need to see their  best at hundreds of meters deep. To accommodate, their eyes have a much  rounder lens to refract light underwater, as well as teardrop-shaped pupils which can expand to 25 times  their original size. This lets in as much light as possible, helping them pinpoint their prey in  even the dimmest conditions. But once they’ve closed in, they rely on something akin to a sixth  sense to actually catch their meal. Their whiskers, or vibrissae, are composed of keratin  and full of nerve fibers that run deep into the connective  tissue of their face. Sea lions have full directional control  over these whiskers, which can lie flat against their face,  or stick out at a 90-degree angle. When properly tuned, these whiskers can sense the slim trails  of moving water fish leave in their wake. And they’re precise enough to let  blindfolded sea lions tell the difference between objects less  than two centimeters different in size. With these tools a healthy sea lion can catch generous helpings of fish such as anchovy, mackerel,  and squid on every outing. And with their exceptional memories, they  can remember multiple hunting grounds, including those they haven’t  visited in decades. This memory also extends to breeding  territories and birthing areas, as well as which neighbors  are friend and foe. There’s even evidence that sea lions  can remember how to perform tasks after 10 years with no  practice in between, letting them navigate old stomping  grounds with ease. Yet despite these incredible adaptations, there are changes unfolding  in their habitats too rapidly for sea lions to handle. As climate change warms the oceans,  certain toxic algae species thrive. This algae is harmless to  the fish who eat it, but for the sea lions which  ingest those fish, the algae’s domoic acid can trigger  seizures and brain damage. Changing ocean conditions keep  this algae blooming year round, causing more and more sea lions  to wash up on beaches. This tragic discovery is just one  of the many ways the health of aquatic animal  communities can help us better understand Earth’s oceans. These red flags help us take action to protect ourselves and other  maritime mammals. And the more we can learn about the  changing ocean that sea lions inhabit, the better equipped we’ll be to help  these clever creatures thrive.