Leth thinks they should continue looking for Zora, and since the bridge is on the river, that's as good a place to start as any. He is wary of being followed or led into a trap, though, and thinks they should take every precaution to be sure they are not being tracked on their way to the bridge - perhaps someone could detect or dispel magic, just in case someone has unknowingly cast some kind of magical tracking or scrying spell? I don't know if such a thing exists, but it wouldn't hurt to try haha
Upside of taking the boat: Fastest way to get to the Bridge.
Downside of taking the boat: We won't really be able to search the banks along the way, and there will be other people on the boat; perhaps people who could be watching us.