After receiving the CANOE, you are free to travel the Rivers that lead to Gurgu Volcano. Navigating the Rivers is tricky, and you could end up in ElfLand if you don't know where to go. There is only one path to reach Gurgu Volcano. If you follow the river from Crescent Lake into the mountains, go west at the first intersection, then north, east, west, and west again. (On the return trip, you'll want to head south at the first three intersections, then east, and finally north.)
The Rivers on the southern continent are patrolled by a variety of dangerous creatures. You'll most often run into groups of CARIBES or HYDRAS. The CARIBES are similar to SAHAGS in that they have high Evade but don't post much of a threat. HYDRAS, on the other hand, have three dangerous attacks and plenty of HP. They lack much in the way of defenses, though. The rarer OCHOS are like Poisonous HYDRAS that trade a bit of attack power for better defense.
The most dangerous creatures on the Rivers are merficully rare. GATORS have two immensely powerful attacks despite their diminutive size. You can spare LIT2 spell slots on the way to Gurgu Volcano to soften these guys up, because you'll want to take them out as quickly as possible. If you brought a HOUSE to use at the Volcano, you can make your life much easier on the rivers by using spells liberally.