By sea

Every year, the Gulf Stream carries eel larvae northwards from the Sargasso Sea near Bermuda. Storm waves sweep some of them into Lake Wallace, where the freshwater triggers their slow change into adults. During rainy weather, eels slither overland into Sable's freshwater ponds.

Because they must return to the Sargasso Sea to breed, these eels are not isolated from others of their kind.

American Eel
Anguilla rostrata

Eelgrass plants or seeds from mainland estuaries are carried to Sable by currents. Storm waves wash them into Lake Wallace. These eelgrass plants produce seeds, but they are probably not isolated because new plants continue to arrive.

Zostera marina

Tropical beans from the Caribbean drift northward in the Gulf Stream and wash ashore on Sable. The climate is too cold for the beans to germinate. Countless other plants and animals wash ashore like this, but cannot survive.