The Rapids of Dunan (デュナンの急流, Deyunan no Kyuuryuu) are a series of rapids that block off Liukan's Hermitage from the rest of the Toran region via the Dunan River. The rapids were considered uncrossable by a normal boat and have indeed wrecked many a regular vessel that has tried to traverse the swirling vortex.
During the Gate Rune War, the Toran Liberation Army gained the aid of Gen and Kamandol to cross the rapids successfully. The rapids were eventually traversed with the use of the Prodigy.
References
- Gensosuikoden Kiwami Encyclopedia, page 76