Hatchlings and young animals avoid swimming in the sea where they are in danger from predatory fish. Marine iguanas frequently cuddle together at night to reduce nocturnal heat loss and to avoid predation. Females and young forage primarily on exposed reefs at low tides, while the larger adult males feed subtidally on the submerged algae. The iguanas spend the first hour or two after sunrise basking in the morning sun and then move to the reefs or into the sea. If the tide is high during the morning some may feed at sea, while others feed on the reefs.
Activity slows between noon and late afternoon.
The iguanas seeking shade if the sun is too hot. Just before sunset many retreat into crevices or beneath boulders. Virtually throughout the entire Galapagos Islands. On average, El Ni o occurs every 12.3 years, although the 1982 to 1983 event was the most severe for around 100 years. El Ni o is caused by a failing of the trade winds resulting in an increase in sea temperature of about 4.3 C along with an increase in sea levels and precipitation.