Eels are interesting critters. I grew up fishing the Atlantic, and we caught them all the time, the very same species you guys have seen in freshwater. They're a pain in the butt when you hook them, as they tend to turn themselves, and your line, into one big slimy knot. Their spawning habits are amazing. It's hard to believe, and it seems not many people know this, but ALL North American eels spawn in the Sargasso Sea (a section of the Atlantic near Bermuda). Here's a little blurb about them from Virginia Tech's Virtual Aquarium. Emphasis mine.

www.cnr.vt.edu/efish/families/anguillidae.html

The American eel is the only eel species found in frewshwater rivers in North America. Adults are catadromous and migrate downstream to the Atlantic Ocean and spawn in the Sargasso Sea (near Bermuda). The young are ribbon-like (leptocephalus) larvae which float and swim for 1-3 years in the ocean before returning to freshwater. As they near freshwater they transform into "glass-eels" (a transparent form of the adult) which then turns into an "elver" (dark, minature version of the adult), and finally into an adult. Adults migrate upstream and inland as far as Minnesota, and may remain in freshwater for as long as 15 years before returning to the ocean to spawn. Adult eels (up to 4 feet in length) live in rivers where they hide in the mud by day and forage at night. Their ability to breathe air allows them to mover overland around dams and other obstructions. A growing aquaculture industry is harvesting elvers to feed and rear in tanks to adult size, and selling adult eels as food fish, fresh or smoked. The flesh is firm and well flavored, and it is considered a delicacy in Europe and Asia. Virginia is a major exporter of American eels.