In biology class we were told that the eels we caught in creeks and ponds had emerged from eggs suspended in the ocean, specifically the Sargasso Sea, the southwestern part of the clockwise gyre in the North Atlantic—an idea that required more faith than imagination. We know that freshwater eels reproduce in the ocean because larvae have been found drifting near the surface thousands of miles from any shore. Eel larvae—tiny, transparent creatures with thin heads, bodies shaped like willow leaves, and outward pointing teeth—were thought to be a separate species of fish until 1896, when two Italian biologists watched one in a tank metamorphose into an eel.
Eels are relentless in their effort to return to their oceanic womb. I can tell you this from personal experience because I've tried to keep them in a home aquarium. The morning after the first night of my attempt, I found eels slithering around the floor of my kitchen and living room. After securing a metal screen over the tank with heavy stones, I was able to contain them, but soon they were rubbing themselves raw against the screen. Then one died trying to escape via the filter outflow. When I screened the outflow, eels banged their heads against the glass until they had what appeared to be seizures and died. That's when I stopped trying to keep eels.
They're wondrous in their ability to move. They show up in lakes and ponds and postholes with no visible connection to the sea, leaving the inquisitive shaking their heads. On wet nights eels have been known to cross land from a pond to a river by the thousands, using each other's moist bodies as a bridge. Young eels have been seen climbing moss-covered vertical walls. In New Zealand it's common for cats to bring eels to the doorsteps of farmhouses, having caught them in grassy paddocks.
"How many animals are there that live in such diverse habitats?" David Doubilet mused while photographing eels in New Zealand, knee-deep in a spring-fed creek, watercress dangling from his mask and snorkel. "Here we have a fish that is born in the deepest, darkest depths of the ocean, and yet here you have them in a farm paddock with cows."