It's absolutely amazing," said tourist Karalee Brune, a nurse from Livermore, Calif. "I love pelicans, but you cannot get anywhere near this close to a pelican rookery on the mainland."
"It's unreal," agreed Rachel McMillan, 20, the youngest of the group who was touring the Galapagos with her aunt from Memphis.
"It sort of feels like, you know, I'm at the zoo or something watching an exhibit," McMillan said. "But then, I realize that this is reality. I'm in their natural habitat, watching them live their natural lives. It's incredible."
Carmen, the guide, was always watching carefully over her flock. As we toured the island, we begin to understand why the Galapagos is called a living laboratory of evolution.
There are wonders everywhere: a lava lizard here, a Galapagos mockingbird there -- and 13 different species of Darwin finches, so named because it was the different shapes of finch beaks found on each island that inspired Darwin's theory of evolution.
"We are a group of islands that are not too far from each other, but they are far from the mainland so the animals had a time to change, they adapted to a new environment, they evolved into a different way," Guzman explained. "So we have all these species of finches that look very similar to each other. However, the shape and the size of the beak changes a lot according to the kind of food that they find in the place where they live."
Roger Bower, a retired high school biology teacher from suburban Detroit, called the islands "unbelievable."
"This is the world that you talk about every day. The animals are fantastic," he said.
He teaches evolution in his class, a subject that he says is difficult to explore with some students.
"Lots of kids have the attitude that it's going to interfere with their religion or their ideals," he said.
What he is seeing on the Galapagos confirms that his teaching about evolution was right on target, Bower said.
"Things do change," he said. "Animals do change, plants change and here they change pretty rapidly."
It is easy to see why the Galapagos Islands were named the very first World Heritage Site when the United Nations began the program in 1978.
Everywhere we go, there are other boats and other tourists.
Our group leader, Barry Boyce, first came to the islands 21 years ago. Back then, there were 40,000 tourists visiting the Galapagos a year. Last year, there were 161,000 tourists.
"It's very, very typical," said Boyce. "It makes it more difficult and more challenging to organize your walk. You have to figure out where the other guides are gonna go and try to go the other way. Once upon a time, you had the islands to yourself, so it's certainly more challenging these days."
Nowhere is that more apparent than in the main city in the Galapagos: Puerto Ayora. Forty years ago there were just 3,000 residents on this vast chain of remote islands. Today, there are 30,000, and half of them are in Puerto Ayora. Yet there is no sewage system, and the trash dump gets bigger and bigger.
Officially, Ecuador doesn't allow citizens from the mainland to resettle in the Galapagos without a permit. But good jobs are plentiful on the islands and a rarity on the mainland of this very poor country, so people find a way.