Aaahhh!!! This is the reaction most of our guests have when they snorkel with sea lions. This morning our route took us to a small islet known as "Champion" on the northeastern coast of Floreana. The highlight of the day is neither the islet, nor the great variety and number of fishes we snorkel with, but the sea lions. The pups and juveniles we find in this site have a ball playing with us in the water. I never know who has more fun, them or us. They almost show a smile as they approach you at high speeds and just before they touch you, they turn away leaving your heart beating faster. Sometimes they blow bubbles right before your eyes and other times they just remain below you doing some sort of water ballet which truly makes me jealous.
Sea lions are well adapted to the marine environment. They have well developed senses, but, the most efficient is their eyesight as they spend long periods of time diving while foraging in dimly lit waters. Under low light conditions in air or underwater, the pinnipeds' (the order in which walruses, seals and sea lions are placed) pupils dilate in large circles to let in more light. On the other hand, in bright sunlight the pupils constrict to a narrow vertical slit. They all possess strong ciliary muscles for contracting and dilating the pupil. Their eyes are light sensitive and hold a large numbers of rods, which are photoreceptor cells in the retina that respond to low light. They bear a specialized layer behind the retina that contains specialized crystals that makes the retina reflect light like a mirror. This layer is known as the "tapetum lucidum", its function is to send the light that passes through the retina a second time, doubling the available light.
The eyes need a shield against underwater pressure as they dive to great depths. A membrane called "the nictitating membrane" is like an internal eyelid, which also helps in wiping away sand and debris. The eyes also need lubrication, the role is played by the lacrimal glands providing them with constant tears to help protect them from seawater and sand.
Today is the day we encountered dozens of these playful creatures while we snorkeled. We ended snorkeling with a smile, a smile almost as big or even bigger than the smiles on the faces of the wonderful and peaceful sea lions.
