Marine Iguana: Where and when to dive with them

When diving with marine iguanas, respectful observation is paramount. These animals are protected by Ecuadorian law and are part of the Galápagos National Park. Divers must maintain a safe distance, generally at least 2 meters (6 feet) from the iguanas both in and out of the water, to avoid disturbing their natural behavior. Never attempt to touch, feed, or chase a marine iguana. Their unique adaptations, such as sneezing to expel excess salt, are fascinating to watch but should not be interfered with. Spotting cues underwater include looking for their distinctive dark shapes against rocky seafloors, often clinging to rocks while feeding. They are also easily identified by their dorsal spines, which are visible even when submerged. Pay attention to areas with abundant algal growth as these are prime feeding grounds. When they are swimming, their undulating body movements are quite distinctive. Divers should move slowly and calmly, avoiding sudden movements or loud noises that could startle them. Remember, they are cold-blooded, and their time in the water is often a balance between feeding and maintaining body temperature, so minimize disturbance to their foraging and thermoregulation efforts. Ethical diving guidelines mandate leaving no trace and taking only photos, ensuring these remarkable reptiles continue their unique existence undisturbed.

The best time to encounter marine iguanas in the Galápagos Islands, particularly observing their aquatic behaviors, is generally during the warm season from December to May. During these months, the water temperatures are warmer, ranging from 24-30°C (75-86°F), which makes diving more comfortable for both humans and iguanas. Warmer waters also contribute to higher algal growth, providing more abundant food sources and encouraging longer and more frequent foraging dives by the iguanas. While marine iguanas are present year-round, the dry season from June to November brings cooler waters due to the Humboldt Current, which can lead to reduced algal growth and shorter foraging periods. During the dry season, iguanas may spend more time basking to regulate their colder body temperatures. For divers specifically hoping to witness the iguanas actively feeding underwater, the warmer months offer the most reliable opportunities, especially around Fernandina and Isabela Island's western shores.

Marine iguanas, *Amblyrhynchus cristatus*, are endemic to the Galápagos Islands, making them one of the most distinctive reptiles divers can encounter globally. These fascinating creatures are uniquely adapted to a marine existence, thriving along the rocky coastlines and intertidal zones of the archipelago. Their primary habitat includes the shorelines of islands such as Fernandina, Isabela, Española, San Cristóbal, Santa Cruz, and many of the smaller islets. They prefer areas with plentiful algal growth on submerged rocks, which forms the bulk of their diet. While primarily terrestrial for basking and nesting, they are frequently found *in* the water, especially during feeding forays. During high tide, they are often seen clinging to submerged rocks or swimming gracefully through the shallows. On land, they bask on dark volcanic rocks to absorb solar radiation and regulate their body temperature after cold dives, often congregating in large groups. Juveniles typically forage in the intertidal zone, avoiding deeper, colder waters, unlike their adult counterparts. Their entire life cycle, including breeding and nesting, occurs within these coastal environments of the Galápagos.

The marine iguana's diet consists almost exclusively of intertidal and subtidal algae and seaweed. They are herbivores, unique among modern lizards for their marine foraging behavior. Divers will observe them grazing on red and green algae that grow on submerged rocks. They use their sharp, tricuspid teeth to scrape algae off the substrate and their flattened snout aids in this specialized feeding. While they prefer red and green algae, they will occasionally consume brown algae when other food sources are scarce. Juveniles and smaller individuals typically feed during low tide in the intertidal zone, accessing algae exposed by the receding water. Larger adults, however, are proficient swimmers and will dive to depths of up to 15 meters (around 50 feet) to access more abundant algal beds, sometimes remaining submerged for over 30 minutes. This specialized diet is crucial to their survival in the Galápagos, showcasing a remarkable evolutionary adaptation to their isolated island environment and the available food sources.